In my understanding it happens in registrationapp’s registerPatient.gsp, here precisely.
Now that I look at this one again(1), I indeed wonder if the "size" property is ever read before invoking ui.includeFragment(..)…
Probably not 
(1) I’m saying ‘again’ because I have banged my head on another fragment’s configuration issue with the registrationapp’s. See ‘How to use “manualFields” with a “field/personAddressWithHierarchy”’.