AbsoluteLayout.LayoutBounds units

I have an image which I want to place at an absolute position on the screen.

        <Image
            Source="{Binding Mark}"
            AbsoluteLayout.LayoutBounds="{Binding MarkPosition}"
            AbsoluteLayout.LayoutFlags="None" />

On iOS and Windows Phone the position has to be in device pixels. On Android (at least on my Nexus 10 and Sony Xperia Z1 Compact) it has to be device pixels / 2.

It is not device independent pixels as a Android developer would expect (and which would be a good idea in a framework targeting many very different devices). It is not device dependent pixels like on iOS and WP. It is half that number.

• Is this a bug which will be fixed in a future release?
• Is it the same on all devices so that I can rely on it?
• If it is different on other devices or it will be fixed in a future release, how can I calculate the value I need?