Do you have sufficient vertical screen space for more icons?

I just checked here and it seems to be following the setting just fine, but if there isn't room it will cap it at whatever it thinks will fit.

Ahh, so it isn't that it only shows 8, it is that it never shows less than 10.

The reason for that is the number of items you have on the right hand side.  It will allocate sufficient space for them and while there is space under run, it isn't big enough for another entry which is why it is that size.

If you disable some of the right hand items you will find the number of icons on the left will reduce down to 8.

So in your case you would like it to show just the 8 and then blank space even if there is room and the menu has to be bigger?

We opted to fill the space as we couldn't see any advantage to leaving the blank space.