How to dynamically display a result when capture a single value in one of 2 different slicers?

I have a Calendar Year column and a Fiscal Year column in the date-dimension table.

I put them in 2 slicers as follows.

I put 2 cards together as the following example: the big value (i.e. 64) that can be got when select a single value in slicer_1 or slicer_2;  the small value (i.e. 'LY: 74') that is for the previous year when select a single value in slicer_1 or slicer_2.

I want:

• when select a single value for Calender Year, only dispaly the small value for the previous Calendar Year;
• when select a single value for Fiscal Year, only display the small value for the previous Fiscal Year.

For example, here when select 'FY 2018-2019' in slicer_2, only display the small value for the previous Fiscal Year 'FY 2017-2018'.

I guess there could be a IF function/expression for this previous stuff. But how to write it?