I'm looking for the formula used by Salesforce on Data Type: Auto Number fields.
I assumed it was sequential (increases by 1 from the last number generated), but according to our data, it doesn't seem true:
Record created 7:32 AM = 0003288395; Record created 9:06 AM = 0003289295. An hour an a half later and the number is 900 higher. According to a report of all records created and sorted by this number field, there are no numbers in between them unless 900 records were deleted - which I confirmed is not the case in our Recycle Bin.