What is the latest version of this game? In my GOG client it shows that I have 1.08(HOTFIX2) installed, but for some reason I found in my downloads folder two files named:

setup_rebel_galaxy_2.6.0.11.exe
patch_rebel_galaxy_2.6.0.11.exe

1.08 hotfix 2 is what the download page says, which you could have looked at yourself if you own the game.

Those strange numbers you have, look like GOG's old version numbering system and without asking GOG, it is hard to tell which game version they are.

Yes, that's what too says Galaxy.
Ingame, the french version tells in bottom left corner it's "Version 1.08b"