Oh FFS not this again. YOU DON’T NEED THIS
If you want to KNOW the order that Users signed up just sort them by Created Date. Hooray know you know. BUT WHY DOES IT FREAKING MATTER!?
(Answer: It doesn’t.)
If you REALLY want to create asymptomatically increasing serial numbers you can do it in Bubble but it’s WAY above your pay grade if you’re asking how to do it here.
Start here:
THEN read the ENTIRE thread and don’t come back her until you can prove that you have.