MM stands for Middle Markers, meaning it's an event designed for people who aren't the fastest and who aren't the slowest.
For a normal CTT event you pick the fastest 120 riders and the 121st fastest gets cut, but there are also slowest 120 events where the reverse happens. A Middle Markers event is for those somewhere in the middle, so in this particular case you can't have a LTS (personal best time over the Last Three Seasons) of quicker than 56:00 for 25 miles.
MM stands for Middle Markers, meaning it's an event designed for people who aren't the fastest and who aren't the slowest.
For a normal CTT event you pick the fastest 120 riders and the 121st fastest gets cut, but there are also slowest 120 events where the reverse happens. A Middle Markers event is for those somewhere in the middle, so in this particular case you can't have a LTS (personal best time over the Last Three Seasons) of quicker than 56:00 for 25 miles.