Why does KeyEventArgs.KeyCode show a set of invalid keys when debugging?

When processing an event, the KeyDownkey is Delete KeyCodedisplayed as

RButton | MButton | Back | Space

I can determine from the listing Keysthat

RButton = 2
MButton = 4
Back = 8
Space = 32

Delete = 46

and

2 + 4 + 8 + 32 = 46

But why is that?