Understanding TECS.SP

My plane does not have an airspeed sensor, so I’m looking at TECS.SP to see what APM Plane thinks the (calculated) airspeed is. However, if I plot the values on a graph, it’s an almost perfectly straight line, showing ~16m/s, even while on the ground:

Am I correct in using this value? I’m trying to determine why APM is throttling up just before touch-down, causing it to overshoot.