His numbers are actually a little off.
it seems the error is that his calculation is not taking in to account fractions of a percent. You can test this yourself by putting in the hashrate box, for example, 30 and 30.999, and seeing they produce the same result.
I think he did not do that intentionally and perhaps he made a bug with his code. He got nothing by intentionally code to reduce Reorg risk a little bit like this.