How long did it take your adopted cats to come out of hiding?

Hi everyone! I have just adopted a beautiful orange boy (around 1 yo) and brought him home from his foster home. Since he came to my apartment (Sunday night, it's currently Wednesday morning), I only kept him in the bedroom, and he has been hiding under the bed. He comes out at night, uses the litter box, explores the room and meows a bit, but he is spending the entire day hidden under a bed in a "loaf". I keep his food and water under the bed, too, so he has easy access, but it's very hard to tell if he's eating. He peed and pooped both nights, so he must be digesting something (?) but the food is not missing visible amounts.

So my question is, how long did it take your cats to come out of hiding/start eating more normal amounts? I try not to be an overly anxious first-time cat parent, but it's definitely starting to worry me.

For context - he is a former stray cat, so a little naturally shy, but he was rescued off the street when he was still a kitten nursing from his mom.