I might be misreading the graph, but it's over a span of 40 seconds.
Looks to be in a 1200 fpm (feet per minute) climb for 20 seconds, then descends rapidly (1000-5000 fpm!!!!) which leads to airspeed increase.
Altitude listed is MSL (Mean Sea Level), not AGL (Ground Level), and if we looked at a chart the terrain around the site is probably 1300ish feet above sea level.
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