I stopped looking long ago but to my limited understanding, when V says it does X in 1s, it means they delegated the job to gcc faster than others doing the whole work.
Either that or V author is up for a few ACM turing awards.
If you mean the table under "For comparison, space and time required to build each compiler", I think, that it is about what each compiler took in time and disk space to compile itself, on the same hardware, so it is about P compiling P sources.
V can not compile C or Go, Go can not compile C, and C compilers can not compile V or Go, so it can not be otherwise.
Either that or V author is up for a few ACM turing awards.