If a member has purchased more than one product from you, the order of which they are displayed in their library will resemble the position of the Products in your Products Dashboard. 

Changing the order of your Products in your Members library

Rearranging your Products in your Products tab will change the positioning of the Products purchased by your Members. 

If you wish to change the order in which your Products are displayed for all Members, simply rearrange the Products displayed in your Products tab.

Keep in mind, rearranging the order of your Products will impact all Members and cannot be customized for individual Members.