Hello Louise,
The provided screen capture indicates that you were checking quotas under IAM & Admin. The alert-related data is to be found under Billing → Budgets and Alerts.
To check the actual quotas for the Datastore app operations, you should follow these steps:
2) In the left-side frame navigate to “app engine”.
3) On the left hand side frame, you should see "quotas": click on that icon.
4) You should be able to gather more fine-grained information on your Datastore access budget there.
Please let us know if you find significant info this way.