The Page Settings screen sets paper size & controls the placement of the grid on the page.
Adjusting margins also gives you a bit more control over the grid itself:
First, confirm the paper is correctly set to US or International sizes. To do this, open More '•••' to find the controls.
 Set the default for all new papers by choosing 'Settings for New Papers'.
 Or, change the defaults on an individual paper by choosing 'Inch/Metric'.
Next, open Page Settings and make adjustments.
The white area shows the paper itself.
The dotted blue outline marks the margins — sometimes there is a gap between the grid and the margin because GridMaker and QuiltPaper only include full-size rows & columns.