I have been using Day Rover very long time to get to Metrocentre to Sunderland and back every time. It can be confusing when it says Newcastle to Sunderland.
Also Explorer ticket go's beyond Tyne and Wear boarders/Newcastle to Sunderland Line. e.g to Carlisle or Alnwick or Nunthorpe.
Also you can check via Northern Rail Network Map to where the zone are.
RE: Pricing