How do CFIs typically determine proficiency for complex and high-performance endorsement?

I'm working on getting checked out in our flying club's Arrow II. Our club's insurance requires 10 hours of instruction if you don't have any retractible time.

I've done a few hours with an instructor, and he signed off on my complex endorsement, which I also need from an FAA standpoint. So I'm FAA endorsed, but I need more time to satisfy club insurance.

§61.31.(d)(2)(e)(i) says:

(i) Received and logged ground and flight training from an authorized instructor in a complex airplane, or in a flight simulator or flight training device that is representative of a complex airplane, and has been found proficient in the operation and systems of the airplane;

What defines "found proficient?" What is the list of things an instructor "ticks off" their list to be able to give that endorsement?

Same question for the high-performance endorsement?