I Rent Part of House, How Much Square Footage for Home Office Expense?

Starting in September, I began renting 2 rooms from my landlord, and I've been using the second one as an office for my little YouTube business. My landlord lives with me, and we share the house with another roommate. I'm calculating the home office expense, and when it asked for the "Entire home square footage," do I actually include the whole house? Just the 2 rooms I rent? Or my 2 rooms plus shared spaces?