For a daily rolling limit, the individual amount spent in each transaction becomes available again after 24 hours. For a monthly rolling limit, it becomes available 30 days after each transaction.
e.g. If you have a daily rolling limit of 500 USD and spend 200 USD at 10 AM and 100 USD at 3 PM today, the 200 USD will become available again at 10 AM tomorrow, and the 100 USD will become available again at 3 PM tomorrow. For a monthly rolling limit, if you made these same transactions on the 5th of this month, the 200 USD would reset on the 5th of next month at 10 AM, and the 100 USD would reset on the 5th of next month at 3 PM.