Child Page Sort Order is used to control the display order of any child pages listed under the Parent group. For this example the parent group is the "Shop" page.
To edit the page sort order, navigate to the Parent page and click Edit (1) and select the Child Page Sort Order from the drop-down (2)
Select the desired sort order from the dropdown, and then click on Save Page to continue.
Next, we recommend you review how to move a page.