What we must do:

But what we see in the app:

Either way is fine

I just hold the AC at arm's length in a horizontal plane and turn in a circle until the light go from amber to flashing green rapidly, then point the nose down and circle until the light flashes green slowly, also known as the DJI Dance !

Have always done Compass calibration as App showed.  

QuadKid Posted at 2018-5-14 15:25
I just hold the AC at arm's length in a horizontal plane and turn in a circle until the light go from amber to flashing green rapidly, then point the nose down and circle until the light flashes green slowly, also known as the DJI Dance !

That is exactly how I do it.
Never had a problem except when I was standing over a metal medallion in the ground that was covered by the Landing pad.

HedgeTrimmer Posted at 2018-5-14 15:31
Have always done Compass calibration as App showed.

But the fact that text and pics must be in accordance, right?

And now I see another inconsistency: the manual says to turn the a/c nose downward, but pic shows it upward, no? The a/c nose is where the camera, right?

QuadKid Posted at 2018-5-14 15:25
I just hold the AC at arm's length in a horizontal plane and turn in a circle until the light go from amber to flashing green rapidly, then point the nose down and circle until the light flashes green slowly, also known as the DJI Dance !

Put it above your head. The higher the device the better it is for the compass. There might be some magnetic interference in the ground that you may not know about.
Its also easier and (arguably) less strain on the gimbal - the further out your arms are the more strain on the centrifugal spin.
PS. I have done it nose down since the P1 days. I do think DJI got lazy in the app (think how a phantom looks from the side - its similar on all sides). Dji would rotate phantom image 90 degrees. I assumed they just applied the same template with the mavic and never bothered checking.

METROID Posted at 2018-5-14 16:13
But the fact that text and pics must be in accordance, right?

And now I see another inconsistency: the manual says to turn the a/c nose downward, but pic shows it upward, no? The a/c nose is where the camera, right?

No argument from me about Manuals should agree with Product and Software.  But reality hits.
I went with App, because I know how manuals tend not to get updated.

Want to see messed up documentation?  Look at some of scrawlings that hardware engineers put out after they have written diagnostics (go/no-go tests) in machine code.  

Hi METROID, thanks for your suggestion, this has been forward to the related team, hope it will be improved in the future if possible. Actually, as the floor 2# mentioned, both of the methods are fine to calibrate the compass. Thanks again.

Both of this two methods can calibrate compass, thank you for your feedback ,we will modificate instructions, and keep it the same with app.