An inmate is a person confined to an institution such as a prison or hospital, and a canteen is a restaurant provided by such an organization to feed them. region=us&q=inmate In your example, a credit is the ability of the inmate to obtain food from the canteen based on the fact that he has prepaid payment into some sort of account (similar to a bank account) or that payment will be made in the future. Example: I've got unlimited credit.
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