High Overdraw Problem On Android Device

When we profile our game with "Adreno profiler" on android devices, It showed a very high Average Overdraw in Frame stats(About 130.x),And we try to profile some other games, it just about 0.7-3.0x. And even we build a empty scene just with a plane, the average overdraw is higher(About 168.4X).So could anybody tell me what's the problem?
BTW: When we check the overdraw in sceneview of unity, the object's color is accumulated even if it's blocked by other opaque object(Opaque Queue with ZWrite On),so is the overdraw showed in sceneView not conside the z-test(depth test)?

 

About the the overdraw："Scene complexity can be increased by overdrawing, which happens when "an object is drawn to the frame buffer, and then another object (such as a wall) is drawn on top of it, covering it up. The time spent drawing the first object was wasted because it isn't visible."（From：https://en.wikipedia.org/wiki/Fillrate）,if i'm wrong ,please help me fixed it.
And i take a screenshot of a simple scene,the average overdraw showed by adoreno profiler is "52.70x",Which make me confused（But the overdraw display seems right-ScreenShot_2).I don't know it's a problem of adreno Profiler or Unity.

 

I have met the same problem when debug application which made by Unity 5.4 using "Adreno profiler 4.0".
It cost 49.5x overdraw even in a simple scene(a cube only).
I dont know should I ignore it or "PUSH A BUTTON" to fix it?

 

Adreno profiler test some game published by Unity 4.6 is right, but some game published by Unity 5 is wrong.
Why?