With apologies for the long delay before I’ve been able to find the time to look at this, I can now tell you what’s going on here. The problem is that the processor that draws octave lines makes an assumption that it will be able to draw the sequence of characters that make up the label at the start of the line using a single font style as a single string. It therefore disregards the scale factor defined in the Music Symbols editor and uses the font style size instead. It would be quite involved to change this, unfortunately, so I think that what we will look to do in future is consider adding a dedicated font style for octave lines, so that you can set the size of the glyphs it chooses to use by editing the size of that font, rather than by trying to scale the individual entries in the Music Symbols editor. Sorry for the inconvenience!