Is it possible to register as an independent or as unaffiliated in PA? If so, then those numbers might be possible.
No. In fact Here is the Link where for the 2004 PA Registration Stats. Yow will see there is a clear category for Libertarian, Green Party and lastly "Others" Which I would assume to be Independent Voters.
http://www.dos.state.pa.us/bcel/cwp/view.asp?a=1099&Q=444853&PM=1