By default, the Proposal reports in SIX sort alphabetically by Manufacturer. If you want Items to display in a particular order, you will need to use the customized Proposals attached to this page or create your own report, details of customization are in the video.
These reports were set up to use Custom Field 1 to indicate the priority of sorting Items and it is set to sort ascending. You can use numbers or letters to choose your sort order.
The screen shot below shows the default alphabetical sort order: