What's maximum stay under a Ireland visit visa a year?

I got visit visa approved on 23 Sep 2014, and this is my second time for Ireland visit visa.
I arrived at Ireland on 19 Oct 2014 and I asked for to stay here on my application form when I applied visa is 87 days but I was stopped by the immigration officer at the airport.

The immigration officer at the airport told me on Ireland visit visa can't stay more than 90 days a year so basicly I could stay here for 4 days because I was here with my first visit visa for 86 days already

but the immigration officer,he did me a favor to stay here more than 4 days so I permitted to stay here 1 month and I have to show him my new flight ticket soon on 29 of Oct.

I'm not sure about those informations because I did not see any notice on website about maximum stay under Ireland visitor visa is 90 days a year and if it's true I have no idea why the ireland embassy granted my visa because they should have record about my previous visit visa.

I’m not really sure how I could do to extend my visa.I read on website and they said I should contact at the gardar station to ask for if I can get extend my current visit but I contacted a guy at the Gardar station in Cork city already and he said nothing he can do,because I did over stay visa already???

Hopefully somebody could give me some information to get extend my current visit.Thanks in advance
PS.I have to apologise about my English language,I'm not English native speaker.

90 days for each visa but the immigration officer has the right to choose the length of your stay and even to decide whether or not you can enter the state... but if you have strong ground to extended your stay to its maximum period 90 days, go to GNIB at 13-14 Burgh Quay. hope this helps.