This is more to do with your TV-Out rather than Daphne.
Most TV's "Overscan" - that is, all the edges of the 'screen' are just off the display (think of it as a 5% Zoom-in). This is completely normal and standard for Tv's. You only notice it when hooking up PC's as they make use of every corner of the screen.
You need, if possible, to adjust the Tv-out properties of your graphics card. I know ATI cards have options to adjust the amount of overscan and re-position the screen for Tv-out.