Hi...new here! I see all kinds of different serial numbers for Gucci...some have numbers with a dash on the top line, some have only 4 numbers below and some have the same number of numbers on the top and bottom line. The authentic ones I have seen all have 6 numbers on top and bottom. Are the others that don't have the same number of numbers on top and bottom all fake or at one time did they format them differently? Thank you!!