Magento 2: Subtract commission To The Store from the grand total

I have placed the commission amount on the checkout page. but we need get final the grand total after Subtract the grand total. any one can help me for that.

Code is $amount = (int) (number_format($mazeOrder->getGrandTotal() * 100, 0, ".", ""));

Like: $amount = (int) (number_format($mazeOrder->getGrandTotal() - getCommissionTotal() * 100, 0, ".", "")); But it is not working.

Many Thanks