According to this forum post by Loco15:
https://forums.kronosaur.com/viewtopic.php?f=30&t=8952

600Res.jpg
600Res.jpg
george moromisato 10 Aug 2020:

Fixed in 1.9 Beta 2. For low resolution (which is technical not supported) we scale from 768 down to the device resolution (see 600Res.jpg attachment).