What you're calling a reference number is just the date and time in the format date("Y-z-B"). They are the same, because the invitations were issued close enough together in time. So, it's no surprise that in each case, the same person issued the two invitations with the same date and time.
What you're calling a reference number is just the date and time in the format date("Y-z-B"). They are the same, because the invitations were issued close enough together in time. So, it's no surprise that in each case, the same person issued the two invitations with the same date and time.