Read/Write usage of DynamoDB Cloudwatch alert creation

Hi, I'm trying to create a CloudWatch alert triggering when Consumed(Read/Write)CapacityUnits surpass 80% of Provisioned(Read/Write)CapacityUnits for DynamoDB. For this purpose I used the following metrics:

e1 = Consumed/PERIOD(Consumed) e2 = 100*(e1/Provisioned)

Alert should trigger when e2 goes over the 80.0 value. Is that a correct approach to the matter?