I don't know what Mm. means. It can't be beats per minute because it's not possible to have 4-6 beats per minute.
At least according to https://en.wikipedia.org/wiki/Bar_(music), "Mm." can also stand for measure numbers. Presumably, the rhythm workshop wants you to repeat measures 4-6 when you practice.
We need context. Maybe this method has it's own system of speed categories. Maybe it's just 'Measures'. Maybe it's a misprint. I can't see any connection with figured bass and chords though. Pity about the dumb '8ths = triplets' notation when doubtless they want Swing. If this is percussionist training, they ought to know the difference between swing and triplet shuffle.
(EDIT:After reading the comment below from @JimM)
OK, problem solved. It's the rhythm of measures 1 & 2 of the music that follows. Thanks, Jim.