I've already taken the 291 didn't pass, now as I am back to studying after a summer break

I can't remember if there were any class A subnetting questions, i mostly remember class B
reason for asking, Ii'm back to burning a custom subnett chart into my brain, that I can jot down as I first sit down for the test, and I am wondering should I really drill down on the number of hosts for class A for each subnett, I know I should know them and I know how to find them, but class B is like cake to me, class a has larger numbers
should I devote a few minutes to burn these numbers into my brain as well