In the сurrent drawing prefences -> length factor exhibited a value of 0.5.
I enter in the command prompt line size @20.
Choose Tools -> Dimension -> Aligned, paint dimension line on a drawing and shows me the number 10. This is wrong, should be shown in accordance with the scale (factor length).
How to fix this error the program?
The program QCAD is not, it shows the size correctly.
In LibreCAD Length Factor manipulates the distance written in the dimensioning against the real value. So a line with a length of 20 units will be shown as 10 if a length factor of 0.5 is applied. If you measure it with the measuring tool it still will be 20. I'm not sure what this feature is good for, maybe if you really want to draw scaled down. Normally in CAD you draw with real world values, scaling down is done in the printing procedure. So normally the length factor should be 1.
The setting General Scale is about adjusting the size of text, numbers, dimensioning elements to the intended print scale. So you can define all your favorite settings valid for all possible scales and just enter the print scale here, for 1:100 it's 100.
That's what in QCAD is "size scale factor".