It probably looks something like this
I think that's the default for DOSBox, though GOG may have made a few changes.
fullresolution= is the resolution of your monitor
windowresolution= is the resolution of the window
There's a YouTuber "philscomputerlab" who did a whole series of "Tweak Guides" about making GOG games look better than the GOG defaults.
The one on ***Space Quest 1 and 2***
might be a good one to start with. As long as you make a backup of your game's dosbox.conf file before tweaking, you can't mess it up too badly.