My brain must be broken lately. I blame the new infant to the household. I know math, I swear I do!This sort of matches the 1 and 1/2 proficiency zone with a bit less math. Btw, 1.5 rounded down is 3 4 6 7 9 not 3 5 6 7 9. The difference between +1 and 1.5 rounded down is 1 point at level 9-16, then 2 points at level 17+. While this is somewhat important, I don't find it important enough to care. And, intentionally, "+1 if you have proficiency" stacks with expertise (or even another 1/2 proficiency ability).