This should be scrollable vertically because of the padding.

This padding represents, within the scrollable overflow rectangle, the box’s own padding so that when its content is scrolled to the end, there is padding between the end-edge of its in-flow (or floated) content and the border edge of the box. It typically ends up being exactly the same size as the box’s own padding, except in a few cases—such as when an out-of-flow positioned element, or the visible overflow of a descendent, has already increased the size of the scrollable overflow rectangle outside the conceptual “content edge” of the scroll container’s content.