Fare/Zone Question Maynooth-City Centre

[Paddy Junior]

Hi! Can someone explain the difference between inner short hop zone and short hop zone and why does Maynooth appear in both zones? Last week I asked for a 3 day inner short hop rail only ticket between Maynooth and the city centre so I could have the flexibility of getting the train home to Maynooth from Drumcondra/Connolly/Tara St/Pearse Street and was charged €17.80. Having looked at this website I think I should have only been charged €16. I've also just got a student travelcard so should I expect to pay €19.50 or €22.50 for a weekly ticket for Maynooth-Dublin. I think the counter staff are just as confused as I am about these zones. Can someone please clarify it for me? Many thanks, Paddy Junior.