The GST box is for the GST included in the fees in the first box. The remittance fees differ based on the type of service they are providing: Remittance rates for businesses that provide services
This General Information for GST/HST Registrants explains the Quick Method of Accounting and how to elect to use it to calculate your tax payable. It does not apply to public service this link has a list of the rates the reserves deducted is for professional services. Some people deduct the fees in 2020 for future work done in 2021.
If additional guidance is required, it would be advantageous to Contact the Canada Revenue Agency.
