Mersenne: What criteria are the cause for work that gets discredited?

[CARLETON GARRISON]

I had the recent occassion to see a Double Check LL test - find a factor.  On George's top producer page (the one that gets updated less than daily or even possibly weekly - how often does it get updated?), it says that finding a later factor or an incorrect LL result will cause loss of credit.  Is this up-to-date stat policy?  Does this apply only to LL stats or is it possible to lose credit for factoring if later factoring proves more successful?  How many such scenarios are there?   Thanks, Carleton Garrison