Ortho line length

When I draw an orthogonal line, if I specify a distance, it draws twice that distance. Is there a reason or I might be dong something wrong?

I assume you have activated Snap Distance, then the Distance box in tool options bar belongs to that.
See https://librecad.readthedocs.io/en/latest/ref/snaps.html?highlight=distance#snapping

Do you already know the user manual search function?
https://librecad.readthedocs.io/en/latest/search.html?q=distance&check_keywords=yes&area=default