Conditions for requisition line grouping

How requisition lines are being grouped into 1 PO line, 1 Schedule, and 1 Distribution when using Buyer Work Center (Document Builder)

I understand following two profile options, decides whether to create 1 PO line for each requisition line or not, but when does system group schedules and distributions?

1. If PO: Default Requisition Grouping is set to "Requisition", this will create one line for each requisition line. (The profile option will only work with Buyer Work Center, for core forms form personalization is required).

    2.If PO: Default Requisition Grouping is set to "Default" or "Null", this will combine requisition lines for the same item, revision, line type, unit of measure, supplier item number, and transaction reason onto one purchase order line.