The rounds need to an even number. With 15, the first picker gets #1 and #1 in the last round. He should have the last pick.
Very good point. Most mock draft tools default to 15 rounds too. Important point for commissioners to remember to have an even number of players on the roster/bench. If you want 25, do 24 or 26 instead. No harm in not using “divisible by 5” numbers.