You will set the unit to source and select the voltage or the current which ever you want to change.
To change the percentage span of the unit you will have to push the yellow shift button
and use the arrow keys to change voltage or current to your 0% or 100% level
when you have it where you want the 0 or 100% you will push the yellow shift button to take it out of shift mode
and then push and hold the 0 or 100% button to set the units percentage.