Flying UA 1612 ord sfo June 8, delayed for 29 min, but the delay reason is 'late inbound aircraft'. However the inbound aircraft ua1013 is arriving 1 min early.

Ua1013 was assigned as the inbound flight at least 5 hrs before the departure time , at that time there was a nonsense time listed with inbound arriving at 10:30pm and outbound departing at 10:50pm.

Isn't this due to an aircraft swap or some type scheduling issue? I don't see how it relates to a late inbounding flight. Any idea ?