Some songs have double arrows to skip to next song and some have skip 30 seconds forward circle. WHY??

I recently reorganized my playlist in iTunes and synced it to my iPhone. I've noticed that all the songs from one artist have the 30-second skip forward circle, while all the rest have the double arrows to go to the next song. All the songs are listed as music, they're being played in the default music app on the phone, and I loaded them onto the phone by syncing with iTunes. "Remember playback position" is unchecked on every song in the playlist and this problem is present regardless of whether the file is mp3 or m4a. I have restarted the phone, crashed and restarted the app, and removed and readded the songs in question, to no avail.