How exactly does this work? Pretty much everything else is explained in the batch editor guide, but masteries being the new mechanic they are, they obviously aren't listed in said guide. Normally I would check the current value and make informed guesses about how it's supposed to be operated, but it's not actually returning any values to speak of, so I'm a bit lost here. It does tell me the current property type is "Custom", although I'm not entirely sure what that means. Any and all help would be greatly appreciated.