It depends on the timing you want. 

Assuming the frame rate (frames per second) is set to the default 30 fps.......

Let's say you want the transition from Pose 1 to Pose 2 to take 3 seconds.
3 seconds * 30 frames per second gives an interval or distance of 90 frames.
Add 90 to the starting point of 1, and you'd apply Pose 2 at frame 91.

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