That's because you entered days of personal use.

There's a special rule if you use a dwelling unit as a residence and rent it for fewer than 15 days. In this case, don't report any of the rental income and don't deduct any expenses as rental expenses.

If the place was only a rental and no personal use don't enter any days of personal use. 

If you use a dwelling unit as a residence and rent it for fewer than 15 days, don't report any of the rental income and don't deduct any expenses as rental expenses. This is called minimal rental use and the income is not taxable.

See Minimal Rental Use

This is actually an office sublet, not a residence.

I did enter days of personal use, but I'm actually not sure that I should have.

I only used the office for business purposes.

You don't have any personal use then.