Yes, it's little bit tricky to understand data filter and display filter.
The method you used is filtering data itself and you can not calculate past data.
Instead, you need to use table calculation with index formula to filter at Display.
To filter display for the latest 6 month, you can use first.
And filter only 0-6 with the sort of "Order date" as "desc" order.
Now you could filter only display.
Then sum calculation also needs to be modified to calculate "Relative 12 months"
[Last 12 Months Sales SM]
[Previous Year Last 12 Months Sales SM]
Thank you Shinichiro, worked like a charm.
You are very welcome.
Already I have a fresh start in the name of "Rolling 12 months from selected Year/ Month filter" can you please proceed with it.
Thanks & Regards,