Question about subtitle etiquette

[Warm Gun]

I'm trying to sub an entire concert movie with French to English translations available online so that I can understand what the singer is talking about. There is one thing I'm unclear on. It's about multiple people speaking. I know there is always a dash when the second person speaks over the first. But I don't think I've ever seen the dash on the top line. Wouldn't that make sense, though, if the first person is still continuing their line?

Here is an example.

20
00:11:02,337 --> 00:11:05,239
Within a one-way world

21
00:11:05,239 --> 00:11:07,881
If it were for me
Within a one-way world

"Within a one-way world" is a single line said through both segments. A kind of chorus comes in at the 05,239 mark with the verse "If it were for me." So wouldn't the second segment be...

-If it were for me
Within a one-way world

...so that "Within a one-way world" stays at the same height? Or do I just leave the dash out?