[WriteLog] red "x" next to serial number

[wa9als@starband.net (WA9ALS - John)]

> QSO as claimed." I guess I must have inadvertently entered an "x" in the
> serial number field while logging the QSO and that signifies a QSO you
don't
> want claimed, such as a DX log entry during SS.

Is that really the intended reason though?  Or is it just that "x" (or any
other letter) is not a valid RST?