Which instances of an instanced command a staging pass keeps. The per-instance tint alpha makes single instances semi-transparent while their neighbors stay opaque, so transparency is decided per instance: an instance is opaque when its tint alpha is 255 (instances past the colors array clamp to white, matching the staging contract). The filter applies at row-staging time — the kept instances' rows are written compacted, and the command's arrays and palette layout stay untouched.