Second page and even character sheets are allowed, but the game have to playable with just the 1st page. Reed the whole rules for this Jam, not just the summary.
I'm at your side...
Let me quote rule 1. : "Submissions must be a fully playable RPG system on a single page".
The allowing of second side and character sheets (and other stuff) should have to be not needed for full playfulness.
FAQ answer; The game can be spread across both sides, but keep the core rules onto a single side. Use the 'back page' for ancillary info such as GM tools. https://itch.io/jam/one-page-rpg-jam-2024/topic/3889509/faq-2024