What does the command "Vertical speed" mean?


My question is more like a general one for every Parrot drone. I noticed that for AR Drone ROS, pyparrot, OLYMPE, and MATLAB Support Package for Parrot there is an argument for the move command named “Vertical Speed”. Specificly, in the documentation of MATLAB Support Package for Parrot (https://www.mathworks.com/help/supportpkg/parrotio/ref/move.html), it says that the vertical speed is

the speed at which the Parrot drone moves along z-axis, specified in m/s

I understand this argument is like “total thrust” but I don’t understand the meaning of the above. My question is the following: if I send 20 degrees to pitch and 1.0 m/s to vertical speed and assume it attains the desired command, is the drone’s velocity in the global Z-axis 1.0 m/s or the drone’s velocity in the local vertical axis 1.0 m/s? In the second case, since the angle between the local and global axes is 20 degrees, so the “global vertical speed” is 1.0*cos(20*pi/180) m/s. I’m not sure which one is the actual case, but my intuition is that there exists a mapping between the total thrust and the “vertical speed”, the larger the “vertical speed” is, the more thrust the drone has.

Can someone share the experience or thoughts about my problem?

I have tested a Mambo with the motion capture system. I sent this command
mambo.fly_direct(0, 30, 0, 20, 3.0)
to Mambo, and the vertical speed in the global frame is exactly 20% of 2.0 m/s. In the meantime, the pitch angle is about 30% of the maximum tilt angle, in my case, 30% of 25 degrees. So I think the vertical motion is decoupled with the other two motions.