DB default quota limit

Hi! Creating a new database whitout changing the default quota (-1) looks like this is unlimited, even if the stats are displaying a bar that's always showing 0%. If you change this field to 0 the stats are displaying "Unlimited" and there is no bar:

On the screenshot the c1 database is using the default database quota, -1, while the c2 is using 0.

Is this correct? what's the difference betweeen the two?

Thanks!