In the runtime the title I saw was: "Aanvraag Documenten" but the fields i saw were not:
I also looked at the corresponding JScript of the XForms and searched for setCaption. But also no success.
Finally thanks to a tip of a colleague i found it. It was at the calling XForm that used the following construction:
I would recommend to use the Caption field of the XForm itself, so that the title is always the same and in one place, unless of course you want the caption to be dynamic.