Binary is just another way of counting. When we count normally, we use 10 symbols (0, 1, 2, 3, 4, 5, 6, 7, 8, 9). When we count in binary, we only have 2 symbols: 0 and 1. Let's write the number of x's; that is, let's write what each number actually means:

1 is x
2 is xx
3 is xxx
4 is xxxx
5 is xxxxx
6 is xxxxxx
7 is xxxxxxx
8 is xxxxxxxx
9 is xxxxxxxxx
10 is xxxxxxxxxx

What happened at 10? We ran out symbols to use. Instead of adding a new symbol that means 10, we now write a 2 digit number instead of a 1 digit number. The first digit is counting the number of xxxxxxxxxx's now, and the first digit is counting the number of x's

11 is xxxxxxxxxx|x (1 xxxxxxxxxx + 1 x)
12 is xxxxxxxxxx|x|x (1 xxxxxxxxxx + 2 x's)
23 is xxxxxxxxxx|xxxxxxxxxx|x|x|x  (2 xxxxxxxxxx's + 3 x's)
123 is xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx| xxxxxxxxxx|xxxxxxxxxx|x|x|x (1 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx + 2 xxxxxxxxxx's + 3 x's)

Same idea when counting in binary, except instead of adding on a new digit at 10, 100, 1000, ..., we add on a new digit at 2, 4, 8, 16, 32, ...

1 is x
10 is xx (1 xx + 0 x's)
11 is xx|x (1 xx + 1 x)
100 is xxxx (1 xxxx + 0 xx's + 0 x's)
101 is xxxx|x (1 xxxx + 0 xx's + 1 x)
110 is xxxx|xx (1 xxxx + 1 xx + 0 x's)
111 is xxxx|xx|x (1 xxxx + 1 xx + 1 x)
1000 is xxxxxxxx (1 xxxxxxxx + 0 xxxx's + 0 xx's + 0 x's)
1001 is xxxxxxxx|x (1 xxxxxxxx + 0 xxxx's + 0 xx's + 1 x)
1010 is xxxxxxxx|xx (1 xxxxxxxx + 0 xxxx's + 1 xx + 1 x's)
1011 is xxxxxxxx|xx|x (1 xxxxxxxx + 0 xxxx's + 1 xx + 1 x)
1100 is xxxxxxxx|xxxx (1 xxxxxxxx + 1 xxxx + 0 xx's + 0 x's)

So 12 is just a way of expressing the number of x's in xxxxxxxxxxxx. 1100 (binary) is expressing the exact same thing. On the sign they wrote 00001100 instead of 1100; the extra 0's in front don't mean anything. They probably just added them so people would know it was in binary and not one thousand one hundred (computers usually operate on 8-digit binary numbers so people familiar with this would immediately recognize it as binary).