Severus felt Al living the memory, absorbing it, dwelling on every tiny detail with the obsessive intensity of focus that was one of the many things Severus admired about Al.
And then, he felt Al's burst of epiphany, at the realisation - glaringly obvious to Severus - that he behaved differently to others than he did to Al.
Of course I do. A ripply of wry, fond amusement. I don't love anyone else. Only you.