Fast fowarding or rewinding MP3s

Hi guys, I have a 2010 Prius V with A/T and everytime I play an audio book that is in the MP3 format and I want to fast forward or rewind, it does not rewind or fast forward by the amount it shows on the display. For instance, I am listening to an audio book and I am 33 minutes and 15 seconds in and I turn the car off, it goes back to the beginning, so I fast forward to 33 minutes and 15 seconds according to the timer on the factory radio. The problem is, I am not actually at 33 minutes and 15 seconds, I am way farther in and I cannot find out where I am in the audio book or file. After playing with this, I found that if I was to fast forward for like 1 minute I would be in my original spot. Can somebody tell me how this works? Thanks for all of your help.

Paul from Chicago