Triying to change storage device

Hi, I’m trying to change my current storage device (1TB SSD, only 60GB are used) to a 256GB USB stick because 1TB seems a bit unnecessary, obviously. I configured it this way initially because the 1TB SSD wasn’t being used, and instead of buying an extra storage device, I just used that. Now that I have a use for it, I tried to change it in the settings > system > storage tab. I received a notification saying that the new device needs to have more capacity than the old one. So my question is, is there a way to change it to the 256GB stick?
Thanks for your help!