When creating a rule and using the advanced options the percentage column needs the ability to be able to be changed to a fixed amount. eg $256.06 each month for insurance is split into $173.11 business, $82.95 drawings.
At the moment you have to work out the percentage manually. You also need to be able to put a fixed amount to one code and the balance to drawings.
As mentioned by @CathieR, you can allocate Spend Money transaction bank feed rules on an amount basis using the Allocate dropdown and selecting Value located in the Advance options for the Rule. Please see screenshot below for more information.