I'm showing 77T is Polaris and the only aircraft in that range is 2786 (N786UA)

N678UA through 683UA are taken.
I see UA has N687UA also reserved, Does that mean another 763 may be in the cards?
FYI: N688UA/N689UA are taken and N690UA is available for reservation, so UA hasn't reserved any more in the 763 range.