What is the time information on the G1000 MFD map during a hold?
It's most likely an Expect Further Clearance (EFC) timer. You didn't mention the aircraft type but there are several references to it online: Garmin service advisory; Seneca V impressions; Archer manual quoted in a forum. My G1000 experience is in a C172 and I've never seen it there (I can't find it in the manual either) but the features are different depending on the aircraft, so it's possible that EFC timing just isn't in the C172 version.