Bandwidth Consumption Graph for Microsoft Teams Usage

Hi all,
When we run report of Web insights of Bandwidth consumption from Zscaler reporting and compare the same with Internet link router interface utilization , we see there is more than 15% difference between usage seen in the graphs.Even if we consider GRE tunnel Overhead it cannot be having so huge difference.So how do we really get the exact utilization on Zscaler location mapped on the site.

Also need to understand if Teams UDP traffic ( Voice and Video Traffic) will be included in web insights bandwidth consumption report?

Please help to clarify the same.

Dear team,
Anyone have feedback or opinion on above query?