Why would Dumbledore feel any triumph?

I’m sure this is small and insignificant but I’ve read all 7 books probably a million times now and this part has always confused me slightly from the 4th book. Harry has just told Dumbledore how Voldemort has come back and how his mother’s enchantment no longer protects him cus Voldemort has his blood now.

I know the text says immediately afterward that Harry must have imagined the triumph in Dumbledore’s eyes but what if Harry wasn’t imagining it? What would Dumbledore have to feel triumphant about?

Small fry bit to get hung up on but I know no one else in here will judge me for dissecting even the smallest bits in the books. I know we all do sometimes lol

I’m sure this is small and insignificant but I’ve read all 7 books probably a million times now and this part has always confused me slightly from the 4th book. Harry has just told Dumbledore how Voldemort has come back and how his mother’s enchantment no longer protects him cus Voldemort has his blood now.

I know the text says immediately afterward that Harry must have imagined the triumph in Dumbledore’s eyes but what if Harry wasn’t imagining it? What would Dumbledore have to feel triumphant about?

Small fry bit to get hung up on but I know no one else in here will judge me for dissecting even the smallest bits in the books. I know we all do sometimes lol