This clock shows 9:50. By how much is the actual time ahead of the time seen in its mirror image?

Mirror time = 11:60 - 9:50 = 2:10. From 2:10 to 9:50 is 7 hours 40 minutes. (4 h 20 min is the gap the other way round the dial; 7 h 20 min and 6 h 40 min are slips in borrowing.)