This is a very SIMPLE explanation for Packets Hacking. (I'm not an expert with it) (If you want to learnt it deeper please google yourself)
Packets are using HEXADECIMAL.
Hexadecimal vs Decimal
Hexadecimal = 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F( 0 to F )
Decimal = 0 , 1 , 2, 3, 4, 5 , 6, 7, 8, 9...