The cloud storage value is based only on the data you have in your Backend Services projects.
The most common scenario for exceeding the storage limit is by the cloud code logs. I see that the storage size is back to normal at the moment, so I assume that clearing the logs reduced significantly the data size.
Usually it takes couple of hours for the statistics to get updated, so that's the reason why you did not see the change immediately after you have cleared the logs.
If you need further assistance with this issue, let me know.
I am sorry for any caused inconvenience.