With Single App & individual CC you are entitled only to 20 GB of space, no additional space can be added.
You can migrate to CC for Teams, it can be purchased with 1 seat also. It gives you 100 GB of space and you can cancel the present subscription - it will not carry any cancellation fee.
This link should help - Cloud technology | Adobe Creative Cloud for small and medium business
Hi Tricia -
I think Adobe should work hard on lifting the limitation for Single App & Individual CC in a jiffy. We needed it, seriously!
It's been a feature request for 5 years. No change to date.
It's clearly not a priority for Adobe.