Custom mock data example

On this page [Mocking Data - TestBox : Behavior Driven Development (BDD)] (Mocking Data - TestBox : Behavior Driven Development (BDD)) there is a section talking about creating a supplier type (custom data).

I have played around with this but for some reason cannot wrap my head around how to make this work and the example does not appear to be complete.

Could someone possibly show me a working example?