Unique AR invoice number sequences per BU

Summary:

Content (please ensure you mask any confidential information):

Currently, We have AR invoice numbers generating automatically as below. All these AR invoices are from PJB.

LE A/BU A : 1xxxx

LE B/BU B: 2xxxx

LE C/BU C: 3xxxx

When we checked the current AR document sequencing for these existing LE/BUs, There is no any setup for application = Receivables. But there are 4 sequence for module = Receivables, Application = Tax, Type = Gapless and Determinant Type = Legal Entity. But, for all these 4, Initial value is 1.

In manage Transaction Source, For Seeded CONTRACT INVOICES, LE field is blank, Copy document number to transaction number is Unchecked, Automatic transaction numbering is grayed out and unchecked.