[davidstone]

Library author here. I'm sorry you found the wording confusing. I was trying to talk generally about the non-library types: things like int and long. The C++ standard guarantees that there exists an integer type that is at least 64-bits large (`long long` and `unsigned long long`), and many platforms support a type like __int128 that is 128 bits large. Unfortunately, the documentation is slightly out of date. clang has some bugs that cause the compiler to crash if you use __int128 or __uint128 in certain situations (which my library uses), so I had 128-bit support on only in gcc. However, my library is currently making use of C++20 concepts, and only a branch on clang supports that enough, so the master version of my library can be compiled only by clang, so the largest size currently allowed is a 64-bit integer (either signed or unsigned, the library handles that for you).

I'll make sure to update the documentation.