What do you mean "but why"?

This helped...now the question is...

But why?

Hey!
'hex' if for hexadecimal numeral system.
While decimal numeral system goes from 0-9 (if you count from 0 to 9 you will find out that there are already 10 numbers. In decimal numeral system the last digit that is equal to '9', so the very next number will be '1'+0, '1'+1 and so on.) The hexadecimal numeral system goes from 0 to F (16 numbers)
here is the first +32 digits:
0
1
2
3
4
5
6
7
8
9
A (is equal to 10)
B
C
D
E
F (is equal to 15 in decimal )
10 (is equal to 16)
11
12
13
14
15
16
17
18
19
1A
1B
1C
1D
1E
1F
20
21
and so on
Hope it helped you out