I have tried your Set with many different approaches. Strange that it still shows Last Year 0.
I turn your chart to straight table to see the values.
I also observe that you have kept Last Year expression at Full Accumulation.
The below expression displays data for Last year though its not the correct way.
Please let me know once you find more about this.
Use a variable and dollar sign expansion in the set analysis with single quotes. Check attached .qvw.
TEST_edit_SJ.qvw 211.0 K