Dimensioning orthographic views in Inventor gives us dimensions aligned to the plane the view is aligned to.
With isometric views the dimensioning will give us dimensions aligned to one of the origin planes. Pressing space while placing toggles between the different planes.
When you have a custom view it is not so obvious as to which plane is required – Inventor gives the option to choose.
Right click before selecting the dimension position and you have the option to choose between part planes, the sheet view plane or any other custom workplane in the model. If you are having difficulty placing the correct dimension create workplane in the model that aligns to the orientation required.