I have already responded you on GitHub, but to keep conversation here complete, I am also copy-pasting that response (https://github.com/Patryk27/Omega2-GPIO/issues/3) here:

I initially followed code written by the Omega team (https://github.com/OnionIoT/fast-gpio/blob/master/include/fastgpioomega2.h#L12) and I haven't really faced it with the documentation.

I believe the reason is that later we're doing a mmap call, which has to be page-aligned (which 0x10000600 is not), but it could be also a mistake in the MT7688's documentation.