Freeing up space · Where your space went
Why did Storage Studio warn me I have only a few days of room left?
Short answer: Space is disappearing fast relative to what's left. Storage Studio weighs the rate against your remaining room and tells you roughly how many days you have at this rate, naming the app when it can.
Because space is going fast compared with how much you have left. Storage Studio warns on the rate, not the size: a big drop isn't news on a drive with plenty of room, but a smaller one is urgent when there isn't much left. It puts that in the one term you can act on — roughly how many days of room you have at this rate.
The notice names the app responsible when it can tell, and says plainly when it can't. To act on it, open What's Using Space, or Emergency Space if you're nearly out.