I am still hugely confused by everyone's advice and have been playing around with the combos myself. Just matching up symbols and somehow to my surprise I've solved half the puzzles. But now I have TEN 3-modifiers to finish *wails*
Best piece of advice I have is to get some pen and paper out and try to match up your symbols (for example, X + X + X = C); there seems to be some kind of consistent pattern but I can't see it, let alone articulate it lol.
But for me, matching up the first 'digits' in the 2-modifier puzzles worked better than matching up the last 'digits'.
(And in real life, I'm seeing strange colours from the green-on-black of that puzzle screen.

)
EDIT: Siniri, definate lag on my end. Must be more users getting on and trying the puzzles, or giving the servers a workout with the 3-modifiers lol.
EDITED AGAIN: I can confirm that the 'incomplete data' 3-modifiers are totally random. Tried the same combo 3x and each time, it spat out a different result. Argh!