math

I'll also either round to get to a close estimate or refer to a known value I'm comfortable with, and then finalize the answer by applying the difference from the original numbers. It's pretty common as far as I know among systems people use. I'm just some idiot online though, so take it with a grain of salt.

The further down the rabbit hole I go, the more I'm questioning what I thought was 'normal' and what is actually a trait. Who knows, maybe it's dyscalculia. I do mix up the number 9 and letter N, for instance in a reference or ID number I have to remember.