Background Box Changes Size Randomly In .ass Format [Subtitle Edit]

[Subtitler92138321]

Hello, I made a background box using .ass format, here are its settings: https://imgur.com/a/MNvnQ9R
For some reason, when I apply it to all of the subtitles, the box changes its height sometimes. For example: Subtitle 1, Subtitle 2.
I've noticed all of the SE-box-bg lines have different content, even though they're supposed to be the same: https://imgur.com/a/ESEqT5T

I'm new to subtitling and would appreciate any help, thank you so much!

[jagabo]

It's not random. The subs are being padded by a fixed amount, six pixels above and six pixels below. Subtitle 2 has descenders that make the sub taller than Subtitle 1.

[Subtitler92138321]

Okay, in that case, how do I make the box have a fixed height?

[jagabo]

I don't think you can.