Define Gesture detected direction(APDS9960)

I’m a new user at arduino.
Here I found some problem about the principle of gesture detection in user spec.
As show below. When the Downward motion happens, the up photodiode(Up 0xFV) would sense the IR light reflected by the object.
However the figure shows the down photodiode(Down 0xFD) get the IR signal first.
I am not sure weather I explain the figure correct.
I am very confuse about this problem.
I think that your information will give me a useful help.

Here I found some problem about the principle of gesture detection in user spec.
As show below. When the Downward motion happens, the up photodiode(Up 0xFV) would sense the IR light reflected by the object.
However the figure shows the down photodiode(Down 0xFD) get the IR signal first.
I am not sure weather I explain the figure correct.
I am very confuse about this problem.

Image from Original Post so we don't have to download it. See this Simple Image Guide

...R

Are you using this with an Arduino?

If so please post the Arduino program and a sample of the output from the program.

Also post a link to the datasheet for the APDS9960

...R

@JiaJinLin, please do not cross-post. Threads merged.