Coming home. Once realized profit clears $25, it's withdrawn from Lighter over the zk bridge (~15 minutes) back to the coin's sub-wallet, where it splits 25% protocol treasury / 75% buyback reserve.
The buyback. When a coin's buyback reserve crosses $25, the keeper buys the coin on its own pool and burns what it bought with the token's burn(). A single tick spends at most $25, with a minimum-out quoted from the live pool price minus 3%: a large reserve drains as a series of ordinary buys rather than one block-moving order.
One number. Buybacks, plus any holder who sends to 0xdEaD on their own, show up in initial supply − totalSupply, the burn figure every page of this site reports. Trading fees themselves are not burned: they are turned into USDG and put to work, which is what makes the buyback bigger.