Ah, OK. You got a bad download, for some reason.
Could be a local issue, if you are not in the US.
Be sure to try downloading that from your own support page
Go to Apple.com, then the support tab. Scroll all the way to the bottom (Downloads & Updates under the Resources list). Click the download there for "Download macOS Mojave 10.14.1 Update"
If THAT download gives you the same error, then I suspect that you have something wrong with your system.
Reinstalling your macOS system would be a good choice at this point.