Hi Jonny,
I think it is only a visualization problem because in the request you are not showing the occurrences column. When you import a variable in Tables tab the PI always takes this variable tab like unbounded. Please, try now to use the Request RFC in a message mapping and you will see OrdersItem will be unbounded. Also, the item tag in the RFC metadata is a clue, because PI create automatically the item tag to deal with tables (unbounded max occurrences).
Regards.