Try to modify your reservation through the website or the mobile app first. If that doesn't work, just tell them that you are a party of 5 when you check in. You may have to wait a bit, but I am confident they will squeeze in your extra person.
You can modify/change you're reservation online or you might just be able to call them and ask.
U can modify your reservation online
They should accommodate you.
I'm pretty sure they can, if they have more room available. I would ask them if it's okay
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