Changes the scale factor so that the DVI page is displayed as near
as possible to its actual size.
The top left corner of the view window will still show the same page location,
unless shifting is necessary to keep within the scrolling limits.
This item is disabled if the view window is closed or already displaying
the page at its actual size.
The scale factor is actually set to the nearest integer equal to the viewing
resolution divided by the Mac screen resolution.
A likely calculation is
300/72 = 4.17, so the scale factor is set to 4.
Because of this approximation, a 3 in wide rule in your TEX input file
won't appear exactly 3 in wide in the view window.
If this is a serious problem then switch to a configuration file that sets
the viewing resolution to some multiple of the screen resolution;
you'll also need a matching set of PK files.
Note that
360 = 72×5.