Moving load applied to wrong member

I am having trouble applying a moving load to a specific member in my model.

The model is a temporary bridge support pier. It is a plane frame. The pier consists of three steel columns, steel cross-bracing in one bay, and a steel pier cap. On top of the cap, I've placed dummy vertical members to represent the bridge girders that will be supported. On top of the dummy girder members, I've placed another dummy member which represents the bridge deck.

I'd like to generate a moving load on top of the member that represents the deck, but do not understand how the "Initial Position" and "Range" inputs work when generating loads. I input a y-range that represents the height of the deck member, but when I generate the loads, the loads jump down to the pier cap member instead. But they don't jump down to the horizontal bracing member for some reason.

Any help would be appreciated!

The file is attached.

CBB Temporary Pier.STD