I have been running the 5/3/1 for several months now, doing the BBB; Big but Boring assistance work, and I like it, but now want to mix it up, and try the Body Builder assistance.

My main question is in regards to the % of weight on the assistance exercises for the Body Builder template. Like for bench press, in the book it says do 4 sets between 20 - 10 reps. Does that mean do one set at 20 reps, then second set 15 reps, then maybe 12 reps, and final is 10 reps ? And would the weight used be all the same, or make each set heavier as the reps go down ?

And approx what % of weight should I use, if starting at 20 reps ?

Thank you