What I do is this:
1) buy the weapon I want and get the code
Arcana Mace for example: 68 9C 5F 01 00 80 84 1E 00 01 00 00 00 00 00 00 00 00 00 FE FF FF FF 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
2) If I want a +25 AM i take the sixth hexa number (80) and convert it to decimal (80h = 128d) then I add 25 to 128d (128+25 = 153) and convert the number i got to hexa again (153d = 99h)
3) Then I change the sixth number of the code to the number I got
New code: 68 9C 5F 01 00 99 84 1E 00 01 00 00 00 00 00 00 00 00 00 FE FF FF FF 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
4) send the new code and it's done!!
But i don't know what to do if the new code has 3 characters....
for example: if i wanted a +150 AM (116h) the new code shoul be:
68 9C 5F 01 00 11 (6)? 1E 00 01 00 00 00 00 00 00 00 00 00 FE FF FF FF 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
or something else.... i don't know where to put the third character
Credits to iG012