Surfaces can be divided by a number of divisions or by distances between divisions.

When the divided surface is selected, the Options Bar displays settings for both the U and V grids. These can be set independently of one another.
Spacing grids by a specific number of divisions
Select Number and enter the number of divisions that will distribute evenly along the surface.
Spacing grids by a defined distance
Select Distance and enter the distance between grids along the divided surface. The Distance drop-down list also allows for a minimum or maximum distance, rather than an absolute distance.