The following procedure is related to all accounts on the new pricing plan. Those on the legacy pricing plan ($1 per month per graph and Knowledge item) do not have a storage limit so this doesn't apply to them.
If your storage goes over the limit, like this:
You can quickly resolve it with the following two steps:
Delete some of the videos, images or documents you've uploaded. These items are mainly in a Knowledge document.
Delete the same items from the Knowledge File Uploads page:
Check your storage again:
If it's still not resolved, repeat the above steps.