Feedback for “Borrow Interest Rate”

I got the account data of SOL spot market. I find that the optimal borrow rate APR is 10%, and in the page https://app.drift.trade/earn/borrow-lend, I get 10.5% APR on the borrow rate curve when the utilization is 80% (which is the optimal utilization). 
Is there any fee I am missing? I just cannot calculate the exact borrow rate as shown in the UI of https://app.drift.trade/earn/borrow-lend