fixing the 4-th broadcasting rule

    4. If an input has a dimension size of 1 in its shape, the first data
       entry in that dimension will be used for all calculations along
       that dimension. In other words, the stepping machinery of the
       :term:`ufunc` will simply not step along that dimension (the
       :term:`stride` will not be 0 for that dimension).

I think that the first and second sentences are mutually contradicted. The word `NOT` in the second sentence is not required.