Everything I know about this:
You're eligible for the $50 credit -- that's for a 24-team league, if there are fewer teams you get proportionately less -- every 5 seasons, and only after the 5th, 10th, 15th, etc. season. If the first time you ask for the credit is, say, after the 7th season, you have to wait until after the 10th to get it, and you also can't ask for any money for seasons 1-5.
At least half the same owners must have had a team in each of the 5 seasons in question.
The commish cannot keep the credits for himself; he has to give it to league members, although he can divide it up any way he likes.
In progs, I think a good idea is for the commish to give the credits to trusted owners who will use that money to either take second teams when necessary, or pay for a new owner's team in his first season.
In non-progs, I figure the best way to divide the money is to have prizes. In my Random Captain theme, I give $20 to the WS winner, $10 to the WS runner up, $10 to the owner with the best team ERA, $10 to the owner whose team scored the most runs.
Overall I think Admin's doing a good job with these credits, and in prog leagues especially they can be a useful tool for commishes.