In the Mountains

You are head judging a Guilds of Ravnica Sealed PPTQ with a store owner (who is L0) as a helper, who is doing deck checks for the first time. You’re deck checking, and your helper tells you the deck he is checking is about half blue cards and half black cards, but on the checklist player has registered 7 Mountains and 9 Forests. He is actually playing 7 Islands and 9 Swamps, and everything else is correct. He doesn’t know what to do and asks for your help.

What do you do?

The player has registered an incorrect decklist that does not match what they intended to play. We can choose to not issue this penalty if the correct basic lands are obvious. They may be obvious once looking at the land counts in the deck, but aren’t just from looking at the list. Therefore we must issue the penalty. Issue a Game Loss for Decklist Problem. Update the decklist to reflect what is actually being played.

Judges feel free to answer on Judge Apps!