As you might know, your JioFiber connection amount is generated as 'unbilled' every day on a prorated basis.
The credit limit is the maximum amount you can go on without paying for your connection and without having any kind of disconnections to your account. This includes billed and unbilled amount. This credit limit can be increased by paying an additional Security Deposit amount or by paying your bills on time for a certain period of time.
Just because you have a credit limit, it does not mean you won't get a penalty if you don't pay within the due date.
Credit Limit is just a way for companies to tell you how much are they ready to be liable for your usage. That is it. Kindly, do not lean on it in any other way, AND ALWAYS PAY YOUR BILLS ON TIME IN ORDER TO AVOID UNFORESEEN CONSEQUENCES.