Subtitles in the web client are comically large - how to specify actual point size?

What determines the actual font sizes used for the display of subtitles in the web client? I know Plex offers 5 different size options (Tiny, Small, Normal, Large, Huge), but in my client, even the “Tiny” setting is too large. And the “Huge” option is … well, I can’t imagine why it’s available at all, since the letter heights are literally 1/3 the height of the video itself; only a few words will actually fit on the screen, obscuring much of the video itself. See screenshots.

I’m assuming this isn’t as desired, and that the font size is actually supposed to be within a logical range of values. But, why is my web client so incredibly far off from what is intended? What setting within Plex translates a “size” name option (e.g. “Tiny”), to an actual display point size?

Playback via web client is taking place on a MacBook Pro 15" Retina. Same behavior across all browsers attempted (Safari, Chrome, Firefox).