Auto mission about landing height?

my quardplane was set a fly plan from automatic takeoff to landing. it can fly according to the expected flight plan in both horizontal and vertical directions. However, when landing, there are some problems with the altitude control. This should not be a software problem. It should be that I set it incorrectly, but I don’t know where to set it.

The fly plan I set was a rectangle, the height of each way point is 50 meters, and the height of the final landing point is 0. However, during the actual test flight, after the plane passed the last way point, it lowered its altitude to about 35 meters near the landing point, and then switched to vtol mode, and then land. I want to know what parameter is used to set the altitude of landing point where the quardplane switch to VTOL mode.

I want the quardplane to land at a lower altitude before converting to a vtol, so that it consumes less power.

[image]
My Q_RTL-ALT=50M,Q_LAND_FINAL_ALT=6m