Like this? I took out the hyphens, but for scanability, I formatted the 'count' with leading 0's

Although, it's not clear to me why you need it since just the row number would be a unique indentifier

Capture.JPG


Option Explicit


Sub AddCountandUniqueIdentifier()
    Dim r As Range
    
    With Worksheets("Sheet1")
        .Range("O1").Value = "Unique"
    
        Set r = .Cells(1, 1).CurrentRegion
        
        .Range("O2").Resize(r.Rows.Count - 1, 1).Formula = "=TEXT(A2,""yyyymmdd"")&E2&TEXT(ROW()-1,""0000"")"
    End With
    
End Sub