Understanding Android's <layer-list>
The values for left, top, right and bottom are measured from their respective edge.
So left=0dp, top=0dp, bottom=0dp & right=50dp will give you a rectangle that is (match_parent - 50dp) wide and not 50dp wide. Therefore larger values for "right" will actually give you a smaller rectangle.
The same would apply to the other value, but these would behave as expected in most cases, its just "right" that might cause confusion.
Either you use px instead of dp or multiply all dimensions by 10.
I'm ashamed to admit that I don't exactly know WHY this is happening but my guess is that it has something to do with densities where 1dp is a floating px value and the ImageView is scaled up.
Expert answer is welcomed :)