How do credits work for members who require upfront payment?
At least for now, credits are not considered when Fabman checks if a prepaid member (i.e., a member for whom you’ve enabled "require upfront payment") can book equipment or turn on a machine. Prepaid members still need to have enough balance for all of their actions.
For example, such a member won’t be able to create a booking if their balance is too low to cover the booking fee – as if they had no credits. (But when Fabman eventually tries to charge them for the booking, any available credits will be used as normal.)