I partially understand you issue. But blending data has some restrictions and the behavior is heavily depends on the data.
Could you attach your packaged workbook (**.twbx) for the community member to start investigation easily.
I agree with Shin - would like to see more data to better understand the issue
but have you tried including something like below to check back 3 months - you would have to tie it to something by to check for sales by salesperson
Check date>>if dateadd('month',-3,Today())<[Order Date] then 1 end
Just a thought
Please let me know