VBA cleanup

Maybe this:

Option Explicit

Sub sModifyColumnA()

Dim lLR As Long, i As Long
Dim sString As String
Dim vArray

lLR = Range("A" & Rows.Count).End(xlUp).Row
ReDim vArray(1 To lLR)

For i = 1 To lLR
    sString = "=IF($A" & i & "="""","""",COUNTIFS($A$2:$A" & i & ",$A" & i & ",$F$2:$F" & i & ",$F" & i & "))"
    If Evaluate(sString) = "" Then
        vArray(i) = ""
    Else
        vArray(i) = IIf((Evaluate(sString)) > 1, Range("A" & i).Value & "-" & Evaluate(sString), Range("A" & i).Value)
    End If
Next 'i

Application.ScreenUpdating = False
Range("A1").Resize(lLR, 1) = Application.Transpose(vArray)
Application.ScreenUpdating = True

End Sub

Regards, TMS