There are lots of ALO's in a state. Each ALO is assigned certain schools. I myself have 10 candidates.
Back to the previous question: You need to look at the appointments as 2 categories. 1) Appointments from SLATES; and 2) Appointments from the national pool. First thing to realize is that ALL SLATES are individuals who have NOMINATIONS from that slate. Example: Your senator gives 10 nominations. Those 10 are on that senator's SLATE. 560 people (example) have presidential nominations. They are on the presidential SLATE. 120 people (example) have ROTC nominations. They are on the ROTC SLATE. Etc... Each Slate is authorized to be charged "X" amount of appointments. Senators and Representatives SLATES are authorized 1 appointment per slate. So; assuming for the sake of argument, that all 435 representative and all 100 senators in the country submitted 1 slate each with 10 names, potentially, that would be 5350 nominees. Reality; that isn't quite accurate because many individuals may be on more than 1 slate. They may have a nomination from both senators and/or their representative. Also; not all senators and representatives might be submitting a slate, because they may already have 5 cadets at the academy currently, and each can only have 5 cadets at the academy at one time. (5 that are charged against their slate).
Now; assuming 1 each from those 535 slates gets the appointment, that still leaves on average about 650-700 more appointments to go. The presidential slate can have up to 100 appointments. The ROTC slate can have up to 20 appointments. There's also a few other military related SLATES. The key word is "UP TO". The academy doesn't have to give 100 presidentials or 20 ROTC slated appointments. Just like there's also UP TO 85 enlisted personnel applying that can receive an appointment. This number is usually closer to around 50. But it CAN BE UP TO 85.
Add these to the 535 appointments (1 each for the 535 senator and representative slates) and you're probably in the number of around 700. That leaves about 400-500 appointments left to be given out. ALL those people on the senator/representative slates, who didn't get that one appointment for each of the 535 slates, will go into the "national pool". From there, the academy ranks all of those remaining individuals from the highest score to the lowest, and they offer appointments as needed to get the class size up to the number they want. (Usually between 1100-1200; but each year can be different because of other federal laws that say how many cadets there can be and how many can graduate).
That is an over-simplified explanation of the appointments. As for a "PRINCIPAL" nomination: There are 3 ways the senator or representative can present their slate to the academy. The majority of them simply present a list of 10 names in no particular order. This is called "COMPETITIVE SLATE". The academy looks at the 10 individuals and the academy picks the individual to offer the appointment to. They have to pick someone. The other 9 go into the national pool. The 2nd way the senator or representative can present their slate is the "RANKED ORDER" method. The senator/representative ranks the individuals in order from #1 - #10. The academy MUST give the #1 nominee on that slate an appointment; IF S/HE IS 100% QUALIFIED. If they aren't qualified, then they go to the #2 person. etc... The remaining nominees after the appointment is offered, goes into the national pool. The 3rd method is a pseudo combination of the 2. The senator or representative will decide on their #1 person. The senator or representative will call this person their "PRINCIPAL NOMINEE". Again, the academy MUST choose this person and give them an appointment IF THEY ARE 100% QUALIFIED. In this scenario, the other 9 individuals aren't ranked. They are competitive. So if the #1 (Principal) nominee isn't 100% qualified and they don't get the appointment, then the academy can choose any of the remaining. The others go into the national pool.
There is a caveat that many don't know. If the academy offers an appointment to the senator or representative's slate; (However of the 3 methods provided), and the individual with the appointment either changes their mind later and turns it down; or between the time of accepting the appointment and going to basic training the individual becomes UNQUALIFIED because of grades, injury, drugs, crime, etc... The academy doesn't have to go back to that SLATE and choose another individual. They can simply offer another from the national pool. And all those in the national pool; usually around 2000-2500 individuals; are competing for around 400-500 slots.
Again; this is partially a simplified explanation. There is so much to the appointment process that I couldn't possibly explain the whole thing to you. Some senators/representative can have more than one slate in a given year because they only have 3 cadets at the academy. Some quite or are kicked out. So the next year, the senator might submit 2 slates. That's 2 appointments. (They are SEPARATE SLATES. Possibly some of the same names on both. Possibly not). And again; any individual given an appointment from the national pool DOES NOT COUNT AGAINST A SENATOR OR REPRESENTATIVE'S Slate of towards their maximum of 5 cadets at the academy.