Helq's reference to the VMD charts is the correct way to go if one uses the disks. If you then set up the measure for consistency--full hopper, powder settled, etc.--and measure ten charges while operating the press, which provides a consistent "jiggle"--you should have a good idea of what a particular disk will dispense.
OTOH, I see no reason why to fiddle with the Lee disks; use the adjustable charge bar they sell. Adjust the bar as needed to get the charge weight you want. Then, test it by charging the ten cases again and weighing the charges; you'll know what the charge weight to be.
This is the routine I use for charging cases with True Blue on my presses--an updated older Lee Turret and a Load-Master.
To be honest, Rodrigo, I can't imagine manual case charging while running a Load-Master--unless you are still trying to get it set up to run smoothly. I run mine using the typical (Pro / Deluxe) Auto Disk measure on the PTED die, with the manual pull-back rod installed, and it is totally reliable.
Are you having trouble getting the Load-Master to dispense reliably?
Jim H.