IBKR Margin Fee

Hi I have been using IBKR to sell CSP and CC for quite some time now using Cash Account, and basically I wanted to dabble in Margin Account solely to sell put. What I am trying to confirm is that assuming I have little cash left and say I sold a AAPL $100 PUT using margin account I won't be charged any margin interests, and I will only be charged interest if it got exercised where I have to "borrow" $10K from IBKR to fulfill it.

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Is my assumptions correct?

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