Question BPM Help For Updating Your Love List?

The song, Updating Your Love List?, has me quite confused regarding the speed of the notes when they come in during the beginning section of the song (before the speed changes the BPM from 90 up to 145). I'm making an Edit for the song (going to make the notechart of the Extreme chart from Diva 2nd), and the beginning has me facing a brick wall. How do you figure out the speed of the notes when they come in slower than the actual BPM? Also, I don't know if the Time Signature or Quarter/Eighth Triplets may have something to do with it (since I've never had to use those in previous edits and that I can never tell when a song has parts that go in Quarter or Eighth notes), so any help for this would be greatly appreciated.