Sounds as if you have a very timid kitten! Not feral as it was raised in a domestic environment and born of a pet cat, but a very shy individual - was he/she (sorry I know that you cannot possibly know the gender if you cannot get close enough to check but I find it uncomfortable to call any cat 'it' if you know what I mean, it sounds so impersonal!!!!) handled much as a little kitten? Maybe if (s)he has not been handled at all would result in more wariness.
It is normal for a little hiding to take place in a new home, my longest new home adjustment was 9 hours for an adult but that was an Oriental shorthair, a very people-oriented and affectionate breed and even in a new environment they will need a cuddle from whoever is around before too long, it's just a matter of waiting for it with that breed but many cats are a lot more shy and can take a month or two to stop being nervous.
If (s)he is eating and using the litterbox then try not to worry too much just yet. Is (s)he in the room where you sleep? You know you are bigger than them and can seem scary when standing up, also if you the big human is happy to go to sleep in the room they are in it means that room is safe, you feel safe, safe enough to sleep - sleeping where they can see you is a really good signal that there is nothing around for them to fear
Sleep = secure place with no danger, nothing to threaten while you sleep, from them, from you, from others. If that makes sense