I tried to duplicate this and I couldn't, whenever I select the portion of the bar and right-click to select View Data from the context menu, the # of underlying rows is correct, whether the measure is an aggregate or a table calc. Are you using this method or something else (for example, using View Data by right-clicking on the datasource always brings up all the rows)?
I realized that the issue is with the data aggregation. I am aggregating over data that has null values, and therefore rows with the null values is also showing up in underlying data.
I am displaying data by a COUNT on Column2 and it shows 2 as the correct number, but the underlying data on clicking 2 shows all 5 records. I think I need to change the aggregation to only show the not null data, but don't know how. Any ideas?
I am having this same issue. did you ever find a solution?