If you need stored material to move to previously billed only when the material has been installed:
1. Under the project settings, you will want to click edit
2. You will then want to change the setting for stored material to "manually adjust amount each month"
3. When you click on the payapp an hover over the stored material, there will now be a pencil button that you can click.
4. A pop up will appear in which you can manually adjust how much moves to the previously billed column and how much stays in "currently stored"