Default PO SSRS Report Hidden values

I have been working on SSRS for a number of years. I would like to ask this question as I do not understand the thinking behind the default PO Report.

In the default PO report, there is a section for the Totals, one is hidden within the tablix group and the other is outside of the tablix group. Can anyone explain the purpose behind this? Why not just make the hidden values to show in the group straight away?

The report can print multiple POs, instead of showing totals for each one it will print a total for the entire report, the hidden fields keep adding the totals of each PO.

At least that it what it seems to me, never worked with this report.