How much margin is needed to short shares ?

Account used is from Interactive Broker.

Shorted 5,000 shares of BAC at $9.02 (SELL) i.e. about $45,100.

Maintenance Margin shown is about $25,000.

So margin is about 55.4% (i.e. 25,000 / 45,100), seems quite high.

Put in place Stop Loss order at $9.20 and Take Profit Limit order at $8.80 (target profit is $1,000).

Within a short few minutes, the position was positive in the money. Manually adjust Stop Loss order tighter from $9.20 to $8.89 to protect profit.

Wanted to sleep soon. so continue to manually tigthen Stop Loss gradually and it got triggered and closed out at $8.86 (BUY). Collected profit $760.50.