What are the 'Unused credits' in a Gift store?

The white box for 'Unused credits' is an estimated calculation of how many credits could be used up if everyone (who has been granted a gift) would buy the most expensive item in the Gift store.  

The number of credits in the 'Unused credits' box has not been deducted from the 'Credits' box and it's just an estimation of the maximum potential amount that could be spent on gifts. (Not applicable to stores on the AI Platform).

*IMPORTANT: The 'Unused credits' box is only visible in a 'Gift Store' and not in a 'Credit Store'.