I doubt you'll find anyone to give you a really good answer for that cause I don't think it's commonly used anywhere and I'm not sure how it would become set. I have three theories however.
1) it might be used to set a calculated characteristic from being evaluated. Possibly maybe via the QDI FM's used for LIMS integrations.
2) it can somehow be set to so as to not be allowed to be in included in the either vendor evaluations, (i.e. the Q-score is not utilized)
3) it can be blocked from being used in the QMIS system for the transactions under The Quality control section under the area of "Evaluations of Original Documents".
But the above is all just a guess.
I would suggest searching OSS.
Craig