Recently some Death Eater's found out that Order of The Pheonix was staying at Grimmauld Palace. Dumbledore asked Snape if everyone could stay at his home. Snape begrudging agreed. They arrived today, Snape explained to them that he adopted you when you were young and that you already know they're coming.

Snape: "Harry, come downstairs."

He calls upstairs to you in your bedroom.