I know its a porn game and worldbuilding probably shouldn't be my top concern, but I have a few thoughts about the Credit system.
At the beginning of the game (correct me if I'm wrong) your character does not know what the Credits are. They do not know how much 1 Credit is worth.
However, in the auction house, the Syndicate uses Credits to pay for slaves. This leaves only a few options for what Credits are.
1) Credits were originally used in BDCC, and an ex-inmate joined (or started) the Syndicate and it became their currency. (unlikely)
2) The Credits were originally used by the Syndicate, and AlphaCorp for some reason is using Syndicate currency in their prisons. (unlikely)
3) Credits are the intergalactic currency, and your character is from a world that was only just recently involved in the AlphaCorp/Syndicate war, like Artica. (Likely. Supported by the Lilac block start-of-game dialog "My planet didn't follow intergalactic law", indicating they only were recently conquered by AlphaCorp.)
4) Rahi's worldbuilding has changed since the start of writing for BDCC. (Likely. I overthink things.)