No plan in tree by subset, but plan does show on sheet?

[EXPODTL]

I have no plan in the tree by subset under A-3 foundation plan.

The plan does show on a separate sheet when highlighted.

Which is correct, this foundation plan or the way the other plans are shown as a separate drawing on the sheet? 

Note that I have 6 exact copies of foundation plan, can i delete the extras?

[EXPODTL]

Enclosed screenshot

[Laszlo Nagy]

The Navigator part is not wide enough to see the whole tree structure. Make it wider so the whole list shows. Then you will see the right-pointing arrow to the left of Layout A-3, which opens it down and you will see the Drawing placed on the Layout.

If you go to the Drawing Manager you will see which Drawing has which Source View.

Out of those 6 similarly named Views, see which ones are not listed as the Source View of any Drawings. You can delete those because that means those Views are not placed as Drawings on any Layout.