Now i remember we also had to specify what isobutyl (technically just 1 isobutyl exists (not counting stereoisomers), and other form would be tertbutyl). But giving highest priority and minimising sum were definitely something we were taught.

I was free enough to look it up this time - IUPAC guidelines for organic chem - iupac.org/…/Organic-Brief-Guide-brochure_v1.1_Jun… (or more generally iupac.org/what-we-do/nomenclature/brief-guides/)

Section 7 © Lowest locant(s) for principal characteristic group(s)

Although I also remember just as we completed our unit on nomenclature, all we got was “common names”, now i was supposed to know of the top of my head what a cumene is (which I think is isopropyl benzene (not going to check this one)). Same thing happened with polymers, we were taught IUPAC, and then again, “industrial names”