I'm not sure what this is supposed to do, or why. I change the figure in the box to see any changes, and open and close files, but see no consistent effect.
By the way, after fiddling with it, I've now forgotten what the default was
Double-click on any advanced preference to see an explanation of what it is The default is 20 but it's obviously just a matter of taste, some people prefer 0 to fully make use of their screen. Regards,