I got two confirmation emails — a few weeks apart for the event in May that I attended. Both indicated my run group as “Green” – the first had no number indicated, the second assigned me a number. I had numbers done in magnetic material for the doors of the car (I managed to lose one of the numbers during running the second day).
I hope to attend a later event this year so I have sourced a magnetic sheet to make a new number. Staples has printable magnetic sheets that can be used to make numbers. I saw others with just taped numbers so you should be able to do it the last minute.