Correct way to define Document Numbering for Negotiations?

Summary:

Content (please ensure you mask any confidential information):

There seems to occur document violation, at least, when creating Negotiation from BPA's. Created an SR on this topic, and they requested to change the numbering due following "Please make sure the current max identifier is set to a number which is big enough to avoid this unique index violation." (Error: The purchase order couldn't be created. Contact your help desk.)

Could you deliver more detailed instructions for Negotiation numbering? As per my understanding the system should select the next available number for that procurement BU.

This is the link delivered in SR, and they requested to ask here, in the community for more detailed instructions