It means that all Tracks/Patterns won’t reset at the same time at the end of a 'Master" cycle.

If you had Master setting of 32 with 4 Tracks running thus

  1. 15 steps
  2. 12
  3. 7
  4. 6

Then on Master step 32

  1. would be on its own step 2
  2. would be 8
    3…4
    4…2

Master will now reset all 4 tracks back step 1.

A setting of INF would allow them all to carry on on their own merry way.
Track 1 would reach step 3, Track 2 step 9 & so on.