Pivot Chart - X-axis labels when adding data

I have a simple pivot chart formatted as a bar chart with category data on
the x axis and data on y axis. I want to add a 2nd data item plotted against
the same category labels. When I add the 2nd category the labels on the
x-axis change to a combination of the original labels from the 1st category
(that I want to keep) and some outside labels that are "Count of [new
category]"

Two points :

1) Can I add the data without the x-axis labels being changed
2) How do I change the field setting from Count to Sum for the 2nd category.

Thanks

Dean