MKMapView maximal value for distance?

Question

I have a problem with MKCoordinateRegionMakeWithDistance. I try to specify the distance value via a slider in the preferences of my iPad App.

When I put in more that 963 as int or float, the mapView don't apply the value and takes it's own value.

Is there any maximum value or can I edit the MKMapView that it will take values about 10.000 meters?

Thanks, kind regards, Julian

Edit

Here's some code on request:

  // PreferencesView
- (IBAction)changeZoomDidEnd:(UISlider *)sender
{
    [[NSUserDefaults standardUserDefaults] setInteger:[sender value] forKey:@"defaultZoom"];
}
  // MapView
- (IBAction)zoomToLocation:(id)sender
{
    defaultZoom = [[[NSUserDefaults standardUserDefaults] valueForKey:@"defaultZoom"] intValue];
    [mapView setRegion:MKCoordinateRegionMakeWithDistance(mapView.userLocation.coordinate, defaultZoom, defaultZoom) animated:YES];
}