iOS Google map SDK: Setting maxZoom level issue - ios

Question

I notice when I set the max Zoom level of example to 19, the zoom go up to 20. I don't know why.
It's always 1 more zoom level than the one I set.
GMSCameraPosition *camera = [GMSCameraPosition cameraWithLatitude:23.589571946369546
longitude:58.14204730042655
zoom:16];
self.mapView_.camera=camera;
self.mapView_.myLocationEnabled = YES;
self.mapView_.mapType = kGMSTypeHybrid;
self.mapView_.settings.compassButton = YES;
[self.mapView_ setMinZoom:5 maxZoom:19];
// Creates a marker in the center of the map.
GMSMarker *marker = [[GMSMarker alloc] init];
marker.position = CLLocationCoordinate2DMake(23.168520, 58.008163);
marker.map = self.mapView_;
// ------ add layer
// Implement GMSTileURLConstructor
// Returns a Tile based on the x,y,zoom coordinates, and the requested floor
GMSTileURLConstructor urls = ^(NSUInteger x, NSUInteger y, NSUInteger zoom) {
NSString *url = [NSString stringWithFormat:#"http://www.example.com/%tu/%tu/%tu.png", zoom, x, y];
NSLog(#"url=%#",url);
return [NSURL URLWithString:url];
};

Answer 1

How do you find out the maxZoom is 20? Which version of iOS Maps SDK you use?
I tried the sample hello map application from Google Maps' Github page with iOS Maps SDK version 1.9.1 and put the below code in the videDidLoad() method. It prints the correct max zoom which is 19.
GMSCameraPosition *camera = [GMSCameraPosition cameraWithLatitude:23.589571946369546
longitude:58.14204730042655
zoom:16];
mapView_.camera=camera;
mapView_.myLocationEnabled = YES;
mapView_.mapType = kGMSTypeHybrid;
mapView_.settings.compassButton = YES;
// Create the GMSMapView with the camera position.
mapView_ = [GMSMapView mapWithFrame:CGRectZero camera:camera];
[mapView_ setMinZoom:5 maxZoom:19];
NSLog(#"max zoom: %f", mapView_.maxZoom);