The Multiplier field allows you to enter a number which will multiply all quantities taken off.
The AUTO checkbox to the right of the Multiplier field indicates Auto-Default. If marked, your entry here will be the default in Takeoff (if you change the Multiplier in Takeoff, the Multiplier will return to this default after the next Takeoff entry). When Auto-Default is on, the Multiplier is shown in red in the Options display in Takeoff. If AUTO is unmarked, the Multiplier will remain at its setting in Takeoff until you change it.