Discrepency between wndStyles value and sum of wndStyles components

I have a test to check if a field object is read-only. This works for all 1260 fields except one in my application. It reports that a SysListView32 is read only when it is not. The field is possibly a code-jock list.

My code looks something like

  if (testObj.WndStyles AND ES_READONLY) = ES_READONLY then
    log.Message("Field is read only")
  else
    log.Message("Field is NOT read only")
  end if

When I inspect the field's wndStyles properties the object spy tells me that it has the value 1342281729(&H 50019801)

When I sum the components that the object spy reports

WS_CHILD OR WS_MAXIMIZEBOX OR WS_OVERLAPPED OR WS_TABSTOP OR WS_VISIBLE

I only get 1342242816 (&H 50010000)

The field is not read only and ES_READONLY (2048 or &H 800) should not be listed (which it isn't).

I do not understand why there is a discrepency between the wndStyles value that the object spy reports and the sum of the components it reports. Can you please help.