I generated your area and checked it.
I have the correct values.
Screenshot attached.

What version of RWT are you using?
Please send a screenshot of RWT. I'll check it with your settings.

When I resolve the altitude of a specific point using google maps, I obtain a value that is more than 200m different than the value of the generated terrain.

Those are the map coordinates:
top left: Latitude: 19.04413 Longitude: -98.20457
bottom right: Latitude: 19.026 Longitude: -98.18155

Google map altitude of this point: 19.0340925, -98.1955668 =>2143m

Terrain altitude at this point: 1920.4

Should I manually offset the altitudes with the error at this specific point?

Thanks!
Nicolas.