Fatigue for crafting

How exactly does this thing work? I can craft for 50k on my ARM before fatiguing, then on my CPT I craft for 30k SP and I'm fatigued. What the hell? How does this thing work, and why is it so sporadic? Is it tied to the number of items you synth? If it does, it is probably the most ridiculous thing I've seen. If I can get an answer to this, it would be terrific.

You can craft 80k before fatiguing actualy

if your full week(before it fully resets) isnt up, sometimes you can do even more beyond that(partial resets)
this usualy shows up in the form of 30k before you fatigue again

after a FULL reset though youll always get 80k before you fatigue again