Booking.com shows the amount which guests pay, while Guesty For Hosts shows the net payout you make from a reservation after deducting the Booking.com commission. This is the main reason behind the price difference you notice.
Keep in mind that Booking.com includes all configured taxes as part of the reservation payout sent to Guesty For Hosts. Taxes are not subtracted from the payout amount because of how the reservation financials are shared by Booking.com.