Hi @NLS667,
The purpose of the Invoice and Order configuration field is to generate the random numbers with certain prefixes and suffixes by the developer.
Currently there is no such docs for developer class and developer point of view. For now you can take reference from here,
https://github.com/bagisto/bagisto/tree/master/packages/Webkul/Sales/src/Generators
We will soon add this in our documentation before the latest release.