how to programatically zoom in/out mkmap

Hmm, I know this is a simple question but I am new in using MKMaps in iOS. My app is not behaving the same per launch. I have a map and the title of the page will depend on the number of 'job pins' visible in the map. When I am running the app in xcode it displays the correct number, but when I am running the app by itself it does otherwise (but when i moved the map it changes to the correct number of pins visible in the map). The solution I was thinking of is to programmatically zoom in/out the map - on load. Is there a way to do this? I'm really stuck right now.

Thanks in advance!