There is a pin that can be pulled out and inserted. There are weights on those weights, just insert the corresponding weights. It's simple.

At the beginning, you can do a weight of 20, which means you can't do anything after 20, and you can't do 2 1.

Pay attention to the action must be standard, don't use nonstandard actions to make up for it, or be afraid that others will look down on you. That's useless.