Group Insights - Discrepancy no. of members who read a message shown in dashboard versus full report

[Claudia_Mayer_SHS]

Dear readers/experts,

if we have a look at the group insights dashboard of a group concerning no. of members who read a message (period 7 days), there seems to be a difference of we compare it to the accumulated numbers in the xls full report (same periond).
Are we misinterpreting the data or can you share some tips?

Thx in advance!  

[#2]

@Claudia_Mayer_SHS You need to provide more specifics in order for anyone to provide input.

Group with 100 members. Insights shows that 50 members read messages. Probably not a problem.

Group with 100 members, Insights shows 1000 members read messages. Problem...