This effector randomizes position, scale and rotation with given values (fixed). You can change seed separately for position, scale and rotation. There are also global seed that changes all seeds. There is additive mode (‘Add’-checkbox) that adds random values to current state, otherwise values are overwrited.
Scale group has also ‘Uniform’-checkbox that scales clones uniformly, there is own input field for this. If this checkbox is ticked, you cant use X, Y or Z checkboxes.