Depleting storage can be a big worry for many users. The storage allowance you get along with your plan is only used for documents/files you upload to tasks, projects, invoices, and estimates, etc, in your account. None of your other data consumes this storage allowance.
You can delete any of the uploaded documents in Avaza to free up storage space or alternatively purchase additional storage from your Avaza Subscription page. (Settings > Avaza Subscription for $0.5 per additional GB per month)