countifs=calculate(
countrows ( Table ),
    filter (
        table,
        table[Client Name] = [Client Name]
            & table[Provider Name] = [Provider Name]&[Date Of Service]=[Date Of Service]&[Time started]=[Time started]&[Time ended]=[Time ended]&[billing_codes_and_labels.code]=[billing_codes_and_labels.code]
    )
)