Basic drawing problem

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Hello, I'm using a translator, so the context may be awkward.

I made a drawing and it says there's a problem like this.

What kind of concept is it?

I understand that space1-1 is a problem. But I don't know exactly what's wrong.

I don't know the basics because it's a drawing that was written without basic knowledge.

You can tell me how to search.

Thank you.

error message

floorspace.js floor plan

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Face difference is self intersecting, result will not include this polygon, Initial area of other surface 'Face 245' 91.8579 does not equal post intersection area 3.36774