The factor in any offset represents how many units. For example: 2m in Constant means 2m meters between the object origin of each instance. If the object is 2m wide, setting the relative offset to 2 would mean each instance is 4 meters apart because each factor equals 2 meters (the overall width of the object). Martin’s visual above shows this clearly.
It is best not to think of a relative offset in terms of grid units. Try this: add a Suzanne. Set its array to 1 unit in Relative offset. Shrink down Suzanne. The duplicate instance should scale and also remain close to the original Suzanne. Do this with Constant, and the instance scales from its origin.
