Hello Nicole!
Once the plan generator runs, you can manually move the section planes. Select the plan scene, turn on section planes from the view dropdown, then move the orange one where you want it.
Or, you could trash all of the plan generator scenes and section planes. I’m guessing that you were measuring floor heights from the “sketching context” vs the actual origin of the model. Right click on any axis and choose “reset”. If it’s grayed out you know the axes are representing the origin. Measure your floor heights from the origin point and see if that produces better results.
Let me know how it goes!
Mike