individual widths cannot be set for the menu buttons in the wizard
you will need to modify the menu code after the pages are created to add an inline style to the individual menu items to assign different widths.
for example, when the menu is created, the code for the menu item will look like:
<li><a href="index.php">Home Page</a></li>
you would need to add an inline style to a element to give it a unique width:
<li><a href="index.php" style="width: 80px;">Home Page</a></li>