Color 50 Hz mode.
Normal graphics area is 320x200 in low res mode or 640x200 in med res mode.
Most games utilize only this area but a lot of demos and other scene productions do "open borders" and can draw on a much larger surface.
Not wanting to exclude the demo scene, monitor is setup so that the entire visible area the machine produces is entirely visible.
What this means is there are borders visible when working on desktop and most of the games will not occupy the entire area of the screen.
However, there is no demo or a game which would not be entirely visible if it draws outside the normal graphics area.
This also means there is no need for a special setup application or anything alike.
Monitor setup is done by just booting to desktop and selecting auto adjust with some additional fiddling wih phase control afterwards perhaps.
Pixel aspect is a bit of an interesting topic here.
Community accepted correct pixel aspect ratio is approx. 0.9:1, although many people nowadays expect 1:1 ratio as this is how emulators usually present it.
Hatari appears to use 1:1 exclusively.
Steem SSE uses either 1:1 or 0.909090...:1 pixel aspect when ST aspect ratio option is selected.
My calculation gave me 0.920632:1.
Of course, most (all?) color monitors of the time had horizontal and vertical size adjustment dials, so ultimately the end user set it up to his/her own preference most of the time.
Since with having full machine output width visible, 1:1 pixel aspect ratio was not achievable, I opted for approx. 0.9:1 pixel aspect (0.914:1 to be exact).
Having the monitor run so close to the very limits also results in vertical positioning control having almost no or very little effect.
No noise as in mono mode was typically visible in this mode.
Some pics for comparison (Steem SSE with ST aspect ratio option vs modified Fujitsu B19-7 monitor):