I am replaying the video for your convenience

Falcon 9 first stage by the numbers 

Speed of sound = 343 m/s

Max speed on ascent = 1685 m/s (Mach 4.9 @ 68 km)

Max altitude (apogee) = 166 km

Max speed on descent = 1407 m/s (Mach 4.1 @ 65km)

Stage separation (2:47) to touchdown (9:24) = 6m 37s

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Go back and rewatch the video while paying close attention to SPEED and ALTITUDE 

The Falcon 9 first stage trajectory is quite interesting …