The Partition Size: Average column displays the estimated average size on disk of partitions read from the table.
The Partition Size: Max column displays the estimated size on disk of the largest partition read from the table.
Reading large partitions can have a detrimental impact on query performance, and may indicate that data is not being evenly spread around the cluster. Contact email@example.com if you need further assistance in dealing with partition size issues.
Under the Table Info group, the Partition Size: Max and Partition Size: Average graphs displays estimated maximum and average size on disk of partitions read from each table.