As per SEBI Regulations, settlement cycle for Derivative Segment (F&O) is T+1. If you have sold options, the premium amount will be realized on T+1 day only.
However, on T day i.e. the day you sold the option contract, this amount will not be considered as margin as it's not realised. So, if you open an F&O position, with the option premium, you will be charged exchange penalty.