Lockbox: How to apply hundreds of invoices to a receipt.

As per my understanding we have to use overflow sequence and overflow indicator to apply more than 8 invoices to a receipt.But how it works.For overflow indicator we can set up values from 0 to 9 while setting up transmission format,what are these values for and how to decide which one to set? What is the maximum number of invoices that can be applied to a single receipt?

Thank you in advance for your assistance.