Or:

Private Sub Worksheet_Change(ByVal Target As Range)
    If Target.Cells.Count > 1 Then Exit Sub
     
    If Application.Intersect(Target, Target.Parent.Columns(12)) Is Nothing Then Exit Sub
    If InStr("jn", LCase(Target)) = 0 Then
        Target.Select
        Exit Sub
    End If
    
    Application.EnableEvents = False

    With Target
        .Offset(, -4) = Abs(.Offset(, -4).Value) * (1 + 2 * (Target = "n"))
        .Offset(, -6) = Abs(.Offset(, -6).Value) * (1 + 2 * (Target = "n"))
        .Offset(, -6).NumberFormat = "0;[Red]0"
    End With

    Application.EnableEvents = True
End Sub