Asus RT-AC58U: jffs2 partition is still present

I am running 19.07.4 on my Asus RT-AC58U since a few months back. I was going to upgrade to 19.07.5 when this popped up. The sysupgrade file that I found came from the firmware selector:

What should I do? To be honest, I'm fine with just running 19.07.4 for now, but I'll probably want to upgrade at some point in the future and I'd like to know what this all means.

It's just a warning to remind you the factory fw is still there.
If you want to remove it, follow the step in the hint.
Or you can select force-flash mode to ignore it