can't change size of external subtitles

[finalgirlfall]

so. as of right now, i'm pretty sure all of the media in my library has external subtitles, rather than subtitles that are coded into the file. BUT. when i enable subtitles on a given item, they're really small, no matter what i change in Client Settings. (i did a cursory web search and found this forum post, which is about making external subtitles display smaller than the default. which is completely the opposite of what i need--and at any rate, i tried changing those settings, and it didn't have any effect on how large the subtitles looked!

i interact with the media in my jellyfin server through the web client. 
the server (jellyfin 10.10.7) is on a raspberry pi 3b+ running raspberry pi os 11, installed through the debian repository.
please let me know if you need any other information.

(i'm not sure if any of that information is necessary, but i figure it can't hurt...)

[niels]

It's important to know whether the subtitle is external or embedded in the file doesn't matter that much. The format of the subtitles however can make a real difference. There are text based and image based subtitle formats, the latter you cannot resize or customize.

[finalgirlfall]

It's important to know whether the subtitle is external or embedded in the file doesn't matter that much. The format of the subtitles however can make a real difference. There are text based and image based subtitle formats, the latter you cannot resize or customize.

the only things i've tried to watch on jellyfin so far have subtitles in .srt format (and, for that matter, that's the subtitle format i favor when using external subtitles in general). am i correct that .srt is a text-based format?

[niels]

SRT are text based yes, customization should work on those.

[finalgirlfall]

SRT are text based yes, customization should work on those.

okay. but it's not working as far as i can tell. is there anything i might be able to check in the settings to like, make customization work on them? (see for example the forum post i linked in the start of the thread.)