You want to understand the reason your billing cycle ends 14 days after the last offer ended.
Once a promotion ends, in order to avoid a bad consumer experience, it is granted to the people who already opted into the consumer flow, a 14-day period to claim their rebates.
This means that if someone opted in one day after the promotion ended, this same consumer will have 14 days to finish the process normally.
The grace period ensures a positive outcome for all consumers who started the consumer engagement flow within valid promotion dates.