Supabase gives you the tools, documentation, and community that makes managing databases, authentication, and backend infrastructure a lot less overwhelming.
How long have you had this instance? Are there other instances in the same ORG (they all share diskspace)? Have you been adding and deleting lots of instances in the same org?
Basically something is using alot of disk. You have to figure out what and reduce it or go to Pro if it is normal growth over time.
I just created a new org, hit cancel when it asked for creating a new instance. Then went to general settings of an existing instance, clicked transfer then selected an org and it transferred in seconds.