The tertiary address is the deep fallback. Its job is to be there when the primary and secondary are both under pressure at once, which is uncommon but exactly the scenario a single-address market cannot survive. If you have tried the first two and both are stalling across fresh circuits, this is the address to reach for.
Availability over the window is the lowest of the three at around ninety-eight percent, which still means it is reachable the overwhelming majority of the time. The figure is lower mostly because this address is exercised less, so a brief dip weighs more heavily in the percentage. It is not a warning sign.
Latency reads medium. It may take a little longer to clear the queue and render the captcha, particularly right after a rotation while its descriptors propagate through the Tor network. Patience of a minute is normal here. If nothing renders after that across two or three circuits, check the incident log in case a wider event is in progress.
Same verification, every time. Copy from the board, compare against the captcha, never type from memory. See verifying a mirror.