I used to be an underwriter. The bank will calculate an estimated payment for that account that does not currently have a balance. It doesn't have a balance now, but it will at some point, so that needs to be factored in somehow. They are taking a % of the total balance and inputting that as the monthly payment. They do that with deferred student loans also. The % they use depends on how their risk people view that type of account. The monthly payment they calculate could be much higher than what it will be in real life.