Apple Final Cut Pro 7 - Manual (Page 1164)

Note: This is true regardless of the In and Out points you set for the clip. Even if the clip
has an In point at frame 100 and an Out point at frame 200, the y axis of the clip starts
at frame 0 of the media file and goes to frame 299.
When you choose a value for the keyframe on the y axis, you are choosing a frame from
the clip’s original media file. When you drag a speed keyframe up and down on the y
axis, a tooltip appears that displays which media file frame you are assigning to that point
in time in your clip. As you move the keyframe up, you choose a later frame in your clip’s
media file; when you move the keyframe down, you choose an earlier media file frame.
The top of the y axis represents the last frame of your clip’s media file, and the bottom
represents the first frame.
Last frame of clip
First frame of clip
Length of clip’s media file
(in frames)
The X Axis
The x axis represents a clip’s playback time. Frames are always played back at the frame
rate of the clip. You can set a keyframe at any point on the x axis to specify which media
file frame you want to see at that moment in the clip.
For example, suppose you want frame 100 from a clip’s media file to appear 2 seconds
into the clip. In this case, you set a speed keyframe at 02:00 in the clip. Then you vertically
adjust this keyframe to the value 100.
1164 Chapter 69 Changing Clip Speed