(1) A small clock is 4 minutes away, and the difference of 60 minutes is the difference of 15 hours.

② The maximum number is 1005, because in the serial number of 1005-20 10, 20 10 (maximum) needs two 1005 (minimum) to make up, and/kloc- I'm guessing that if you add any number under 1005, you can make up 20 10, so it's 1005 at most.