It's actually 85 Regular Navy and Marine Corps and an additional 85 Reserve Navy and Marine Corps.
Bottom line, it doesn't matter how many apply -- if you fill out the paperwork and have a positive CO recommendation, then you are very likely to receive one. If 300 Sailors and Marines apply for the SECNAV nomination, there will be 300 SECNAV nominations issued. The Naval Academy chooses how to charge those 85 (out of 300 in the example), something that isn't in your control. It works just like the Presidential...if 500 candidates had parents who served for 8 years (equivalent Reserve points) and apply for the Presidential...then 500 Presidential nominations are issued....but only 100 can be charged to the Presidential nomination category.
This is why all the previous posters have stated to apply to ALL sources. If you don't get a nomination from another source and weren't one of the 85 USNA decided to go with, it just makes the odds less likely. Having a MOC nomination opens more possibilities due to what is codified in law.