Simple mode simply shifts all subtitle cues by the specified value (in milliseconds) below. Enter a positive number to add delay to the cues, or add a negative one to make them appear sooner.

If the subtitle cues are shown at the right time in the beginning but then later increasingly getting out of sync, you can try using the Linear Shift mode to fix them. The most likely cause of this is the subtitle file is intended for video with different frame rate from another source.