The lettering indicates the set (same letter is same set – including super/giant sets)

Rest times are recommendations/ranges. Take what’s needed for the highest level performance (Meat and Potatoes movement will generally be 2-3 minutes rest, upwards of 4-5 on leg movements, most pump work take less than 60 seconds rest)

RIR stands for Reps In Reserve (this is just another variable to regulate the amount of stimulus). 0RIR means the set is taken to failure. 1RIR means 2 reps short of failure. 3RIR means 3 reps short of failure, etc.

Aside from the first 2 weeks of most programs, and recovery phases, pretty much all sets should be taken to failure.