There are a couple of possibilities as to why the deduction is reflected on your return. Per the definition below from Congress of what is included in the Qualified Business Income deduction calculation, one possibility is if you received a 1099 DIV with an amount in Box 5, the dividends from a REIT can be included in the calculation. Another possibility is if you had any 1099 MISC income with an amount in box 7 (non employee compensation), the IRS requires that income reported on Schedule C and it would be included in the QBI deduction calculation:
Per the IRS recently released Notice 2019-07, the following is a definition of the income included in the QBI deduction calculation:
Congress enacted section 199A (the Qualified Business Income Deduction) to provide a deduction to non-corporate taxpayers of up to 20 percent of the taxpayer’s qualified business income from each of the taxpayer’s qualified trades or businesses, including those operated through a partnership, S corporation, or sole proprietorship, as well as a deduction of up to 20 percent of aggregate real estate investment trust (REIT) dividends and qualified publicly traded partnership income.