Hickory, Dickory, Dock
Each mouse was moving from one number to the next every hour. After 6 hours, both would be at the bottom of the clock when it was 6 a.m.
George Schmaltz [firstname.lastname@example.org] gave Minus exactly what he was looking for:
Rodentia would run around the clock moving at a rate of 1 position (each
hour on the time clock) in 1 hour. Micki would be moving at the same
rate. Therefore, they would meet at the 6 o'clock position or at
6:00 a.m. They would meet again at the twelve, then at the six, then at
the twelve, etc.
It only stands to reason that if Micki and Rodentia took three hours to
get to the three and continued at their steady pace, they would come
together at the 6 in three hours and it would be 6:00 a.m.