A .6, .12 and .18 minor version release of Mendix Studio Pro is an MTS version, every .24 minor release is that major version's LTS release.
In your example, 10.18.x is an MTS version of Mendix 10. The last number (.x), for example 10.18.3, is the patch version, containing bug fixes for that minor version.
See https://docs.mendix.com/releasenotes/studio-pro/lts-mts/ for more info on lts/mts
I do agree with the lacking experience of updating, though...
LTS, MTS, and Monthly Releases | Mendix Documentation
Mendix advise us to use LTS versions for all of our apps as it has highest security and stability.