Why is draggable coordinates not exactly containment in array coordinates?

Why is draggable coordinates not exactly containment in array coordinates?

Hello.
Why is draggable coordinates not exactly containment in array coordinates?

See the following demo and notice that left and top coordinates of draggable elemente are between [42,90,392,340] and not [50, 100, 400, 350] as set.  Why's that?


Thanks