What does “You might want to put 30% down for yourself” mean?

Question

In the movie Law Abiding Citizen, there is this dialog when Clyde is having meal in the cell at about 48 minutes:

Clyde: Oh, excuse me, waiter?

[The waiter looks at Cyde]

Clyde: You might want to put 30% down for yourself, my man.

[The waiter kind of nods and leaves]

What does "You might want to put 30% down for yourself" mean?

Answer 1

I haven't seen the film, but I would interpret the sentence as: You might want to add 30% of the bill (as a tip) for you.

Answer 2

"Put down" refers to "putting down a value of 30% in the spot for the tip on the bill".

More generally, "put down" means "write" similarly to "write down". A longer form would be "put down on paper", for example.