If I remember correctly Brewer said "acu rem" meant you had hit the bullseye. I'll
go look again.

It took me a while, but here it is, from Brewer:

Rem Acu You have hit the mark; you have hit the nail on the head. Rem acu tetigisti (Plautus). A phrase in archery, meaning,
You have hit the white, or the bull's-eye.