Instance pay during booking feature works like the following example.

Suppose you set instance pay during booking is 50%. That means you must have to pay 50% of your total cost during checkout. You can pay rest 50% after contacting with admin or by hand or later. You can set the no. of percent from global setting panel. You will find this option from here

Dashabord->WooCommerce->settings->rnb-setting url.

You can disable this option for the setting tab of main product. Go to the back-end of this product and check the Settings->show/hide tab . You will find this option here.