difficult maths for 20 points

The total no. of possible binary strings formed by eight 01’s = 2^8=256
The group of six 0’s can appear from the first digit or second digit or third digit.
There are only 8 possible combinations with six 0’s in between:

00000000
00000001
00000010
00000011
01000000
10000000
10000001
11000000

Hence the number of 01-strings=256-8=248

String is smaller than call so you can't see it!