The numbers aren't tied to the game's completion percentage. Each month a new release comes out. So last December was 13.x, and next December will presumably be 37.x. The weekly bug fix releases provide the numbers after the decimal point, though a lot of those don't get uploaded here. After the second week (so, starting each month with xx.2), the current release is available for free by following the itch.io link.its version 0.25.2 ; is that mean the game only 25,2% completed?
The game is just a bit more than halfway to the 1.0 release, with additional content being planned beyond that. The 1.0 release should occur around the middle of 2024.