How to calculate step if > 1

Is there a way to calculate step which does not throw error and greater than 1
For example, I have 3D image of shape `(512, 512, 110)`, I want to create multiple patches of shape (`128,128,10)`, I don't know what should be the step size? Can I calculate it? 
This line in readme is not clear to me
`(width - patch_width) mod step_size = 0`
