That’s explained immediately after the section you quoted:
Since MST is GMT-0700, the reference time can be thought of as
01/02 03:04:05PM '06 -0700
It’s a simple increasing sequence: 01 02 03 04 05 (PM) 06 07.
Using 03:04 PM rather than 03:04 AM makes it possible to show the two time representations 15:04 and 03:04PM more clearly (this is speculation on my part).