[1 Lucky Texan]

The below assumes you're adding coolant to the overflow tank and this is all recent, you may have needed to 'burp' air from the system since it seems it was quite low.

At this point, you could just keep an eye on the level for the next few days. If it doesn't soon level out and stop requiring fluid, you may have a different issue.

confirm that the radiator fans are operating and watch the gauge - particularly while idling waiting for long lights/trains and under other conditions (exiting freeways, long pulls uphill, etc.) Monitor for odd heater/defroster temp changes.

I'm betting it will be OK. search for 'cooling system burping' and similar info.

 

[1 Lucky Texan]

he said he changed the cap.

I suppose though, there could also be a crack near the rad cap neck.