Reffering to this guide How can I obtain the multiplicity shown in the domain model? Because at some point I need to add a 'Change object' activity and they tell you: "In the menu that appears set the attribute to be changed to be the association between grid entity and image entity, and set the value to the variable name of the new image entity." But the variable cannot be found. EDIT: Line saying "The related reference guide article can be found here." is broken!
You mean this image?
That's the TemplateGrid being used. In it's settings you can define how many columns or rows to show.
As for your other question: A Change Object is done on the NewPizza object, and in that Change action, the reference between NewPizza and NewPizzaImage is set.