losing headcounts while using some columns in parameter FDI

Hello I'm facing an issue while using a parameter in FDI for the subject area HCM - Workforce Core.

below an example when I use this paramater, I get the right headcounts number 2K :

Case @parameter("param")('') when

'Business Unit' then "HCM - Workforce Core"."Business Unit"."Business Unit Name"
when 'Educ' then "HCM - Workforce Core"."Education"."Highest Education Degree Code"
else null
end

but while I use this one, my headcounts got reduced to only 500 which is the wrong number :

Case @parameter("param")('') when

'Business Unit' then "HCM - Workforce Core"."Business Unit"."Business Unit Name"