'On the record' in legal terms means being under oath, eg during a deposition or when testifying in court. A comment like this could be offered as evidence, but the outlandish idea of spending 20,000 years in jail means it could just as easily be taken as a complaint about the unfairness of the charge.
IANAL, but isn't this the kind of offhand comment that frequently comes back to haunt people? I guess its very dependent on which country you're in.