At the moment, I'm working on the subtitling of an anime. I thought subtitles were fine and finished, but apparently that's not the case.

I'm using Aegisub, and here's what the preview of the video with the subtitles (.ass) looks like: what I expected/wanted (normal one).

The link just before is the preview according to Aegisub. After multiplexing the video with the subtitles I wrote, I notice that the video shown by Parole Media Player (I'm on xubuntu) is exactly the same as the preview.

I also wanted to see the result with VLC (with always the same file), but this time the result is very different : what I absolutely don't want (in VLC).

It is as if the size of all subtitles in VLC has been reduced. How is that possible? (Those present on the images are normally font sizes 190, 102 and 59, and in Dyuthi font)
If that's the case, how can I fix the problem? (or an alternative solution)

P.S.: At first glance, there is no problem with the font I use. Aegisub's "Fonts Collector" managed to find Dyuthi-Regular.ttf in my usr/ folder.