Whenever I set the region property of the MKMapKit it doubles the span.

For example:

```
MKCoordinateRegion currentRegion = map.region; // assume the current center of region is around New-York and the span is 2 by 2
map.region = map.region; // assign the region to itself
MKCoordinateRegion newRegion = map.region; 
// the span of newRegion is different (almost twice than currentRegion)

```

what's going on here?