Keep in mind that the view from the nib is being automatically resized as it is placed inside the tab bar interface, so you want the scroll view to go along for the ride, and not stick out off the bottom of the resized view as it is doing now. Thus, you should either place the scroll view higher up in the view, or else use autolayout constraints (iOS 6) or autoresizing springs and struts (iOS 5) so that the bottom of the scroll view sticks to the bottom of the view, so that as the bottom moves up (the view gets shorter), the scroll view moves up with it.
(In the nib editor, you can ask the editor to simulate the presence of a tab bar [Simulated Metrics > Bottom Bar > Tab Bar], just to give yourself an idea of what the final size will be; but the right approach is to use appropriate constraints/autoresizing so that the view can be resized and its contents will still be visible. For one thing, that allows you adapt to both the iPhone 4 screen and the iPhone 5 screen.)