This was the only source I found for a breakdown of the crowd that day. http://en.m.wikipedia.org/wiki/Notts_County_F.C.
Whichever way you look at it there were 22,000 empty seats in the stadium.
According to Wiki
"Notts County also booked their second successive visit to Wembley and their second successive promotion. The Magpies defeated Brighton & Hove Albion 3–1 in front of 60,000 spectators, 25,000 of which were Notts County fans."