J.P. Instruments EDM 740 Pilots Guide - Manual (Page 41)

For Your Safe Flight Page 41
Example C: Aircraft has two MAIN tanks.
When you partially refuel, use:
‘FILL +’: use this to add the amount of fuel you pumped into the
aircraft (it doesn’t matter which tanks you added to - the
EDM totalizes ALL onboard usable fuel). In this example
you will add ‘+ 14.0 GAL’, the same as your fuel slip
reads. This will be added to the totalizer REM value.