2 sentences explain the same thing about std::ptrdiff_t

In 1-ProceduralProgramming/3-Types.ipynb these 2 sentences explain the same thing:

The equivalent counter part for signed integers is the std::ptrdiff_t, which is the signed integer type of the result of subtracting two pointers.

You might also encounter std::ptrdiff_t, which is akin to std::size_t but for signed values. It is typically used in the STL to store the result of subtracting two pointers.

Just one should be kept.