@Nobby @efsdsffs Thats only partly correct. Idk how sierra lee uses it however in terms of general software development it just means major changes.minor changes.patch
1.0.0 does not necessarily mean that the game is finished it can also mean that there was a major change to the existing code that significantly changed things (in order to improve performance, to make the product scalable etc) so in this case if Sierra went back to the existing code and rewrote it in unity or something it would count as a 1.something.something despite the product being incomplete as there has been a major change to the old code making it incompatible. When the product is complete people usually change the first number just to mark a major benchmark in development (since the product is now a finished one) however it does not mean that an incomplete product cannot have a major change.
Usually 1.0.0 marks a complete product on the games seen on this website because the games here are small scale applications and scalability or optimization is not too much of a concern so no major changes are required (unlike enterprise applications or engines or even large scale AAA games) so developers here do not have to make major changes to the code and instead just add content to existing code in the form of updates or patches.
The response was correct with the rest of the information. The second number here is for minor changes which basically mean new features have been added to the current iteration of the product. In the current version 0.37.3 it means that there have been no major changes but there have been 37 updates to the current build that added extra content. The 3rd number just means that there have been 3 bugfixes to the 37th update.
If interested you can check out semver.org which documents the semantics and the history behind versioning in software development.