Fout in Adres 2x Plaats

Hi,

I’m using your plugin, but one translations is wrong.
In the contact form the translation of Postcode comes out as Plaats.
Now I get Plaats twice i.s.o. Postcode and Plaats.
In what file, and how, can I change the translating of the ZIP-code back to Postcode.

Ingrid

http://wordpress.org/extend/plugins/gravityforms-nl/