Could you upload a small sample application to demo your data model and current analysis?
This will help us to help you.
In general, using all records in your current selection within the aggregation is standard behaviour of QV analysis, so a
sum(VALUE) will sum up all values, limited by your date selections and grouped by the dimensions in the chart, but will not apply any different logic like calculating differences by default. So you would need to tell QV what do to, either in your chart expressions or maybe possibly in the script.
But as said, to help you more, I think you need to detail your requirements and settings, the screenshot is not giving enough information to help you.