XL 2010 Somme plage erronée [RESOLU]

Sub Totalisation()
    Dim dl As Long, plage As Range
    With Sheets("synthese")
        dl = .Cells(.Rows.Count, 2).End(xlUp).Row
        Set plage = .Range("C12:C" & dl)
        .Cells(dl + 1, 2) = "Total"
        .Cells(dl + 1, 3) = Application.WorksheetFunction.Sum(plage) 'somme fausse
        .Cells(dl + 1, 4) = Application.WorksheetFunction.Sum(plage.Offset(0, 1)) 'somme juste
        .Cells(dl + 1, 5) = .Cells(dl + 1, 4) - .Cells(dl + 1, 3)
       
        'mise en forme
        .Range(Cells(dl + 1, 2), Cells(dl + 1, 5)).Borders.Weight = xlThin
        .Range(Cells(dl + 1, 2), Cells(dl + 1, 5)).Interior.ColorIndex = 9
        .Range(Cells(dl + 1, 2), Cells(dl + 1, 5)).Font.ThemeColor = xlThemeColorDark1
        .Range(Cells(dl + 1, 2), Cells(dl + 1, 5)).Font.Bold = True
        .Cells(dl + 1, 4).NumberFormat = "#,##0.00 $"
        .Cells(dl + 1, 4).NumberFormat = "#,##0.00 $"
        .Cells(dl + 1, 5).NumberFormat = "#,##0.00 $"
    End With
End Sub