How then could anyone's prayers diminish the number of souls already in hell, let alone reduce it to zero? Best save those prayers for Church suffering and Church militant.
The merciful, infinite God sees and hears the prayer of the long-suffering mother for a wayward son. Though his sins may persuade other men that he is in hell, God sees the son, and the mother who would literally give her life for him.
In the parable of the workers in the field, did the landowner not give the same salary to the men who began work at 3:00 as he did to the workers who began work at 9:00? He pointedly told the complainers that "Did you not agree to work for what I offered you, and can I not dispense my money as I wish?"
We see through glass, but darkly.