Bidder numbers display on the Advance check-in confirmation screen and again in the confirmation email.
If you need Bid Paddles, you have the option of providing a pdf in both confirmation messages which can be printed at home. Of course, some guests will arrive at the event without bid paddle in hand. . . missed the pdf, printed but forgotten, printer was not working etc.
Since you'll have to have a plan for providing new bid paddles to these folks anyway, many customers opt to have a greeter at the door (or set up an express line) to distribute bid paddles to all guests who checked in online.
If you have printed bid paddles (as opposed to handwritten numbers on the back of a catalog), you'll need to pull the paddles of advance check-in guests a few hours prior to your event: Go to Tickets > click on the Bid Number column to sort by number > reference the "Checked In" column to pull the checked in paddles.
Or you can ask guests to print their paddles at home, and simply arm your greeter with cardstock and a large marker to handwrite replacement paddles as needed.
Either way, some guests won't remember their bidder number, so the greeter will also need a tablet, phone or laptop to look up names and bidder numbers. The easiest reference screen is Auction Night > User Status where guest names/bidder numbers display in an alphabetical list, along with a search field.
Note: Advance check-in was designed to work seamlessly in conjunction with pre-assigned bidder numbers, but it is still possible to assign bidder numbers at check-in for guests that do not use advance check-in:
Guests using Advance check-in will be assigned the temporary bidder number associated with their record (similar to pre-assigned numbers) instead of in numerical order. You'll need to pull the paddles of those who checked in online (see above), then you can assign the remaining numbers as guests arrive to check-in. The software will prevent any number from being assigned twice, so no need to worry about an occasional overlap between advance and regular check-in.