I have had this same problem before, as well as now, with compilations
Right click the song and go to 'get info'. Under the 'info' tab there will be a spot to put the track number, i.e. 358 of 500. You will have to do this with a majority of the songs from what I can tell by the few I just checked.
Also, make sure the 'part of a compilation' box is checked.
this has worked for me in the past. Not sure I am willing to try it for all 500 songs though.