Identify the type of sync problem
If every subtitle appears too early or too late by the same amount, a simple timing shift is usually enough. If the sync starts correctly but gets worse over time, the file may need a more careful adjustment.
Watch a few points in the video: the beginning, middle, and near the end. This tells you whether the offset is consistent.
Apply a positive or negative shift
When captions appear before the spoken audio, shift them later. When captions appear after the audio, shift them earlier.
Small changes are easier to test. Try 250ms or 500ms increments, then preview the result against the video.
Use partial shifting for one broken section
Sometimes only one section is wrong, often after an edit, intro, recap, or missing scene. In that case, shifting the entire file can fix one part and break another.
Use a partial shift when a specific time range needs its own adjustment.