A clock shows 4:10. How far ahead of the actual time is the time seen in its mirror image?

The mirror shows 11:60 - 4:10 = 7:50. From 4:10 to 7:50 is 3 hours 40 minutes. (3 h 20 min and 4 h 20 min come from slips while borrowing the minutes; 2 h 40 min wrongly takes the mirror time to be 6:50.)