How to make focus area smaller when using SwiftOCR?

Question

I'm currently working with SwiftOCR and trying to reduce the areas where the camera has focus. The reason is to be able to register for example a receipt, such as receipt number, date and amount. But i want to register one at a time.

Like the picture below.

The idea is that the text will automatically be fed into the correct text field and then be able to register a new one directly.