If a score line is not yet full, but you do want a straight margin, the lines must be aligned. By setting line justification in the layout to a value less than 100%, you indicate that lines must be justified if the line is filled for at least that much percentage.
Line justification 100%. A section at the end of the line remains empty (approximately 70% is filled)
Line justification 50%. About 70% of the line was already filled (more than 50%) so the remaining 30% white is distributed over all notes.
If the line justification percentage is too low, you run the risk that a single measure will be spread over an entire line. Such a size (or sizes) is called an 'orphan'. Because unadjusted orphan measures have proportionally too little white space between the notes, MusiCAD will provide them with the same amount of extra whitespace as in previous lines (see orphan justification under layout)
Line justification percentage is also used with conditional line breakes