the pawl moves a certain distance. its movement can be devided into steps. first is pre travel(before contacting the rachet), second is contact travel(where it pushes the rachet, and cylinder).
with an eight shot cylinder, with the rachet set up to the same degree difference from a cylinder, andsince there are eight of them the rachet steps are shorter, the pawl will move farther before coming into contact with the rachet. the contact time is then shorter, so the cylinder moves less. because the rachet is indexed to the cylinders, when the pawl stops, the cylinder is in the right place.
only one step on the hand will actually contact the rachet, as the length of the ratchets is now shorter.