Help: Is the time to be delay (e.g. 1000 equal to 1 second) or to be advance (e.g. -500 equal to -0,5 second).
Help: Some times the subtitles becames more unsynchronize with the progression of the movie. This two fields allow you to specify the shift in each period (e.g. shift = 1000, period = 5, every 5 minutes the subtitle is advance 1 more second).