ReadonlybackHow many samples into its own past the reference is read — 0 is the same instant.
ReadonlymovedThe aim CHANGED, so the frames taken under the old one describe something else.
ReadonlyrefinedA trusted reading has already moved this aim onto its own arrival.
Carried because an aim must be refined ONCE and then left alone. Re-deciding it every run
would re-decide it on a number that jitters by a sample, and every move drops the frame run
— so a policy that keeps refining never lets a run finish, and the row reports
too-few-frames for ever while looking like it is working hard.
Where to read next, and what it costs.