This setup is aimed at making you pay in the buy menu so you can set the default of payment, there are two settings that you can default from the payment option in the buy menu, which is Now or the second Letter of the payment option that you can choose to default payment in the menu buy.
I. How to Setup Step
Step 1. Settings - Other Menu - Module
Step 2. Module Configuration - Buy - Payment Dialog - Now / Letter
II. Setup Results
If this setup has been done according to the method above, then when you make a Pay it will immediately exit the Letter option.