Simple Guaranteed Strength and Size Program, "Heavier Preparation Sets"?

I understand it for the most part but I’m confused on this part

“On the first two workouts of the week you will do 3 work sets of each exercise as well [as 3-4 gradually heavier preparation sets]”

What does the 3-4 gradually heavier sets mean?
Does that mean for example the first upper day its

Bench 3x8
Bench 3-4x7,6,5

Quite confused here

Are they referring to gradually “warming up”?

Yes, those would be your warmup sets.

It means if you are doing 3x8 at 225 lbs, you would first do something like the following gradually heavier preparation sets:
1x8 at 115 lbs, 1x6 at 155 lbs, 1x4 at 185 lbs, 1x1 at 205 lbs

Of course, you can adjust the rep numbers and exact weights to your needs.