Unfortunately, we do not provide custom bidder numbers or paddle numbers yet. All bidder numbers are assigned across the entire BiddingOwl system and assigned in the order they were received. We are planning on allowing custom bidder numbers in our future enhancements.
However, here is a workaround...you are able to assign paddle numbers.  How they are assigned will depend on the type of auction you are having.
Online OR Silent w/Mobile Bidding Auctions
Due to bidders registering themselves online you, as the auction chairperson, are not able to edit their bidder account. However, you can create a manual list and assign paddle numbers as your guests arrive. This list can be used to record paddle raises as they happen. Your auctioneer/volunteers would note these winners and hand off the winners lists to be recorded, via Auction End > Record Bids, throughout the event. Recording these winning paddles would add them to the winner's overall invoice for payment at the end of the event.
Silent with Bid Sheets OR Live Auction/Paddle Raise
You are able to upload all of your bidders ahead of time, via Bidders > Import Bidders, or add them as they check-in. Use the first name field and add the custom number there before the first name. This will allow you to search for them by paddle number or last name and use them within the system.  These numbers need to be at least 3 digits long.
You would then record the bid manually via Auction End > Record Bids.

If there are any other questions we can answer for you please let us know.