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The icon can be clicked to change to a summation icon which will result in a summation of all time series that only differ on a qualifier within that group. Those time series will be replaced by 1 time series which contains the total value of the summation. A total will appear as 1 time series in the Time Series Dialog:
Qualifier Aggregation
Within a time series set <qualifierAggregation> can be specified, this combines all time series together that have the in the same time series set specified qualifiers. Aggregation can be done by sum, mean, min or max.