Variation of count - between Fiscal Years

Hello Everyone, I am struggling to calculate a variation of count between fiscal years.

1- I created my fiscal year column using this formula.

_FiscalYearNumber_ = if(MONTH('MyTable'[date_column]) <= 9, VALUE(FORMAT('MyTable'[date_column],"YYYY")),VALUE(FORMAT('MyTable'[date_column],"YYYY"))+1)

_FiscalYearText_ = "FY "&Right(Format('MyTable'[_FiscalYearNumber_],"0#")-1,2)&"-"&Right(FORMAT('MyTable'[_FiscalYearNumber_],"0#"),2)

I used the FiscalYearText in the Axis of my clustered column chart

2-  Using  the _FiscalYearNumber_, I can calculate the count for the Actual Fiscal Year... like this (a new measure):

_card_count_A-FY_ = CALCULATE(count('MyTable'[card]),'MyTable'[_FiscalYearNumber_])

Now this is where I am stucked...

How to calculate the Last Fiscal Year: _card_count_L-FY_, so I can make a difference be the two (_card_count_A-FY_ and _card_count_L-FY_) and DIVIDE([_card_count_VAR_FY],[_card_count_L-FY_]) to have the VAR %...

Thank you for your help and insights!

I used this formula... but it does not work

_card_count_L-FY_ = CALCULATE([_card_count_A-FY_],'Mytable'[_FiscalYearNumber_]-1)