Subtitle offset doesn't seem to work

Hello, I’m running Jellyfin as a docker image in my Synology NAS server. Recently noticed the subtitle offset option, but it doesn’t seem to actually change the timing of the subtitles. The slider also resets to zero after clicking away or re-opening the option, leaving me unsure if the offset stayed. Also seems a bit confusing to just call it “+1” or “-1” seconds instead of making it clear which direction delays or advances the subtitles. Maybe a smaller box near the option gearwheel would be better, with two buttons to add or remove 0.5 second increments.