Building vs. Land Costs

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Hi, I'm a newbie so I'll qualify my question a bit by saying it might be a stupid question, but in the post https://www.biggerpockets.com/forums/88/topics/25519-free-property-analysis-worksheet where a property analysis worksheet was provided, the building and the land costs were separated out. How is this split determined? It's in the upper right portion of the sheet in green boxes. Thanks.