What absolute garbage, it defies the entire point of tipping. Is this even legal? If a restaurant got caught doing this, they would definitely lose many customers or even get run out of business.
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.