What arrears are payable ?

I have just been awarded a full contributory pension.It is to be backdated to January 1st 2024. I have been in receipt of a non contributory pension from that time till now. What arrears will be due to me? The full pension amount or the 11 euro per week difference between the 2 pensions? As the contributory pension is not means tested would that be relevant? It is an Irish pension.If anyone is blessed with sufficient knowledge . I was just wondering.

If the difference is €11 per week and you're due c. 11 months backdated then presumably that's c. 48 weeks x €11 = €528? Why not just ask DSP/SW or just wait for the backdated payment to arrive?