Version numbers below world names are replaced by string of code

When I opened up snapshot 18w01a for the first time, when I went to select a world, where normally since 1.9 the most recent version the world had been loaded on would be, there was a string of code, and I did see the version, it was in the middle of that string of code. I have a feeling that there's a small, hard-to-notice, character, like a period or a comma that isn't supposed to be there.