You can only calculate your pension entitlements based on current regulations and who knows what the future holds.
If (based on current regulations) you estimate that you will be entitled to a full Irish State Pension then that's exactly what you will get.
If you also worked in the UK for 4 years you may be entitled to a small UK State Pension. That has no bearing on your Irish Pension and would therefore be payable by the UK in addition to your Irish Pension from the Irish State
Perhaps you should apply to the UK Pension Dept for records of your NI contributions and request a pension forecast