This makes easier to make sure that you are watching/(have found) the correct episode that you were looking for.
You will also probably start noticing that sometimes the seconds are wrong for some entries, please click on the "Edit Anime Information" button to suggest to MAL Anime DB Moderators the correct duration for that anime.
Because you will probably starting using more the button "Edit Anime Information", you may also want to tryhttps://greasyfork.org/en/scripts/407729-better-buttons-to-edit-anime-information
If an anime has the value Duration: 00 sec. per ep., it means that the duration for that anime is Unknown (MAL doesn't have the duration for that anime).
The script only works when you are logged in.