How to explain this test in the problem?

Question

Algorithms

The essence of the problem: find the number of substrings in a string that do not contain another string. Question for this test:

abcdefgh
fgh

You can also find 28 substrings from the first 7 characters ("abcdefg"), and then 3 more from the last two ("gh"), so I get 31 lines, and in the correct answer - 30. Where is the extra substring acquired ?

Answer 1

In your answer, in my opinion, the string "g" is included in both 28 and 3