Hi Ash,
Q) Do I need to put an offset in so to avoid UDN creating duplicate numbers?
A) No. The offset is for convenience, aesthetics and to assimilate with an organisations current numbering, rather than avoiding duplicates.
Note the information from the admin guide:
3.5.4 Numbering Offset
Enter a number here if you want your numbering scheme to start at a given number. This is very useful in cases where you are migrating from a previous system, so that numbering in SharePoint can continue from the point that was reached by the previous system.
Q) What is the best way to find the last assigned number?
A) The only way is by adding a test file. We are unaware of a situation where that is not sufficient.
Q) We had version 2 installed prior; is there a master list of assigned numbers I can access or should look for?
A) There is no master list of assigned numbers. Some of our clients have millions of documents. Having a master list would be unusable and take up too much disk space.
MacroView Support