There are four different default styles for graph windows... the windows that are created whenever you double-click on a subset to view a graph for the data within that subset.  The styles differ in the amount of space that they require on the screen, and, perforce, the amount of information that each can display.

If you have a small monitor, you may which to view small graph windows, which are about one-half the size of the default size (large).  Small graph windows have much less information about the subset and gates than the larger windows.

The medium size is 75% of the dimension of the default.  Finally, you may choose a resizeable graph window.  This window, once created, can be resized to any dimensions (from as small as the small graph window to twice as large as the normal size).

The size of any newly-created graph window is determined by the preference that you have set.  If you want to change the default size, open the Preferences, choose "Graph Window" preferences, and select the new default size.