How to set any specific point to get dimensions for elements

Hi There

Can anyone help me out that how to set any specific point to get dimensions.

As it is visible from image that for dimension 200, first point is fetched from top (circled red) & second point is fetched from bottom (circled green). I want to fetch both points from bottom.

Moreover, when i try to fetch dimensions for horizontal element i get dimension of 0 (circled light blue) which means dimensions are fetched at same distance for top & bottom points.

I have attached graph showing how i have done it. Let me know where to edit.