How to set the display size of the game canvas?

How to set the screen size or rendering size of the game not from cocos creator but from the cococs creator xCode exported game project.

There are bunch of Objective-C, C++ files there and I tried to update their screen values like in AppController.mm I updated the height

bounds.size.height -=100; app = new AppDelegate(bounds.size.width * scale, bounds.size.height * scale);

but it’s not effecting the game display size and it always appears to be in full screen mode.

Basically I wanted to put a banner ad at the bottom of screen but it should not overlay on the game canvas instead it should appear separately form game canvas and do not hide the bottom portion of the game canvas and for this the game canvas need to be in 100px(ad height) less in height

Anyone knows how to achieve this in anyway? I’ll appreciate your solution…