It works out to the same end result (with the exception that waiters usually have some absolute minimum wage they can earn, so if a waiter makes 20$/hr in tips the restaurant still need to pay a bit on top of that.
One super annoying thing about this system and people choosing not to tip is a situation like this, assume a waiter is serving two customers in an hour, the local minimum wage is $9/hr and the sub-minimum wage is $3/hr, the first customer tips $4 dollars, yielding a potential wage excess of $2 (assuming a reliable rate) when the second customer tips $0 then the waiter ends up making no money beyond minimum wage. So if you're a tipper another customer that doesn't tip can cancel out your tip.
I'm not certain how these are aggregated from an accounting perspective, but I wouldn't be surprised if the window was either a full day or a pay period (in the latter case, every two weeks someone totals $3 * hrs worked, adds on total tips and verifies if that number is above $9 * hrs worked (do nothing) or is below (make up the difference out of the employer's pocket.
