When you create a point within a component the Flash player uses the component’s coordinate space. So for example, if your custom component is 200 pixels from the top of the screen and you create a point within it. If you set the point to a Y value of 0 it will be at the top of the component (which means it will be 200 pixels from the top).
Originally I had written a helper class which would recurse its way up the display chain and total up all the values of the X’s and Y’s, but there’s a far simpler way to get the point’s real location.
You can use the localToGlobal function to translate a point’s coordinate space. For more information check out the Adobe docs