Very interesting! Thank you for explaining that, it totally makes more sense now!Senators don't actually have a "district" but there are 435 MOCs who do have a clear district with a number so this is a way to identify the senators in the same system as the House of Reps Members with a two letter state abbreviation plus 2 digit number. The numbers start at a number higher than any state has house reps so that they don't get confused. Thus 81 or 82 or in past years I saw 61 or 62.