yes guys you are right
the main part of APK file which affect on APK size is related to graphic files in folders inside assets\assets\graphics
there is no way to reduce them cause everyone of them is used for special screen size
I have found out that at least size of APK file made by stencyl is almost 3.4MB ( for 1 scene no actor)
and why size is important for me?
cause I want use stencyl to make games for local market in my country (iran) and you know cause we have problem about internet bandwide here, and most of people use 2g for cellphones then size is a important factor here

( its funny when you see somebody has iphone S5 or xperia z2 using 2g internet service

)