Storage for this app is full message

Hi, I have designed the app and I am getting message “Storage for this app is full. Some items may not be displayed”.
How do I fix this. Please help.

Do you have more than 500 rows? If so you need to upgrade to a PRO version.

Did you add ARRAYFORMULA to a column? I did that and got that message. However, I deleted and tried something different, but then hit undo a few times until my ARRAYFORMULA was back but then I didn’t get the storage full message!