Constant SETTLE_SLACK 

const SETTLE_SLACK: u64 = 4;

An anchor predicts from the newest frame every consumer was sent (settle) only within an anchor period and SETTLE_SLACK frames of it, a consumer that took the last anchor. One further behind, for which every anchor would predict from far back and cost every consumer the bits, is predicted past on its own report instead (from the pinned anchor, where it comes to that). The frame where H.264’s frame_num wraps reaches back however far: a decoder that misses it cannot be predicted past.