How should I understand audio levels in FCP7 xml?
How can a keyframe occur at 1252.57 for a clip that has a duration of 766 frames?


Because the user could have used a clip that was longer than 1252 frames, set a keyframe, then trimmed the clip down to 766 frames. If the user later decides to make the clip longer again by changing the out point to a later time, the keyframe will still be in the place they originally placed it. So your calculations should treat the keyframes as they are, even if they are outside of the clip times.