Fixed group by in qlik sense

[meg007]

How can I replicate this formula in qlik sense

{​​​​ FIXED [Supplier Name]:IF ([# Invoices]-([Max Invoices per Month]*COUNTD([Month-Year])))<0
    THEN 0
    ELSE [# Invoices]-([Max Invoices per Month]*COUNTD([Month-Year]))
END}​​​​