is number range unique in SAP

Say, I have a plant 1000 which uses document type NB and number range as 45xxxxxxxxxx0 to 45xxxxxxxxxxx99 for a domestic PO.

I have another plant 1200 which uses same doc type and same no.range for domestic PO. Both belong to the same company codes.

At any point of time, can both PO's bear the same document number or is it unique.

During STO, will there be any problem referencing the PO? or should i create a new document type for both plants.

Thanks

Dhinesh