What's not credible?
Let's say I'm selling you something, say a bag of magic beans, and you don't have cash to pay me. So we agree I'll give you the beans and a tenner in cash (to buy an axe), and you'll pay me x amount of money over y period of time...
Have I given you a gift of the tenner, or is it simply part of the transaction, which is a sale from me to you with a finance arrangement?
Now replace magic beans with digits in a bank account. It's no different.
You'd have to know how the bank account for it to know how it is best accounted for by the punter, but its certainly not a gift, any more than a reduction in interest payments when you refinance a loan with a cheaper lender is.