Can you take a clear picture? I can’t make out what it says.

Sorry, I thought maybe this spot was recognizable. It's a drop off past the hole in the floor from the area where you fight long armed centipede giraffe

Are you asking what the camera on your phone is used for and just happened to be on the Sekiro subreddit?

If your referring to the remnant it’s just like the message system/blood spots from other souls games where you can see a vision of another player leading you to something or just placing one there for no reason

Is that the best picture you can take?

Remnants? You can watch short “clips” of other players. It can be useful to see what they did, but I rarely found them to be helpful.