Original language is only a starting point
A production's catalog language does not list every dub or caption edition. Some stories use several spoken languages, and some animation tells its story with no spoken dialogue. Check the available tracks on the viewing destination. An English subtitle option and an English audio track are different choices.
Text that matches the cut
Confirm the episode, runtime and edition before changing timing. An extended scene or a different opening sequence can put a subtitle track out of step. Where the player provides an offset control, test a small adjustment on a spoken line. If the mismatch keeps growing, the track may not match that edition rather than simply starting a little early.
Read comfortably
Use the player's text size, background or outline controls when offered. Test from the position where you will actually watch. A subtitle that is readable at a desk may disappear against a bright scene when viewed from across the room. Caption tracks that include sound descriptions are useful when dialogue text alone is insufficient.
Sound before volume
Check the selected language and audio format if speech seems unexpectedly quiet. Headphones, television speakers and a receiver can respond differently to the same mix. Raising the overall volume is not always the best first adjustment. If only subtitles are wrong, keep the working video and audio setup while correcting that specific track.