This would be a big difference from the wind speed measurement at mast height as indicated in figure 15 (link also above). An excerpt on 4.1.1.:
A specific measuring campaign achieved an uninterrupted automated flight of 42 h that featured day and night flight with an average power production of 62 kW, in wind conditions varying between 4 and 13 m/s (1-min average measured at a height of 10 m) and estimated wind speeds at flight altitude of 6–19 m/s, showing the robustness of the implemented flight and power cycle automation algorithms and all system components at relevant load conditions.
Also a discussion on Real efficiency of "Crosswind Kite Power" measured at the kite height?.