The analyzer detected a possible error in two or more nested 'for' loops, when the counter of one of the loops is not used because of a typo.
Consider the following synthetic example of incorrect code:
for (int i = 0; i < N; i++) for (int j = 0; j < M; j++) sum += matrix[i][i];
The programmer wanted to process all the elements of a matrix and find their sum but made a mistake and wrote variable 'i' instead of 'j' when indexing into the matrix.
for (int i = 0; i < N; i++) for (int j = 0; j < M; j++) sum += matrix[i][j];
You can look at examples of errors detected by the V756 diagnostic.