Click on the Hole Wizard feature in the tree (or double-click if you don't have Instant 3d turned on) to show the dimensions in the graphics area. Right-click on the one you want to set and choose "Configure Dimension" from the drop-down.
That will bring up a simplified design table.
It will have a row for each configuration. You can edit the value for each configuration as needed. You can also create new configurations from this table. If you'll give it a name at the bottom you can save it for later editing, but even if you don't do that the changes you make there will stay.