I found out, that for my plotter prints, when I get false alarms (my bad, loose cables :P), the progress box shows line ie 120.000, but in Start From the last line number is muuuch smaller, like 100.000. Indeed, when I start as suggested, my pen goes back a lot, so suggested line number there is incorrect!
Edit: It seems that number shown in the "start from" box is the number remembered from a previous not-alarm based stop. Alarm based stops do not remember the last line, which is very bad in context of my pen-plotter!
gSender 1.5.4