The number on the screen is the last twelve months of dividends divided by today's share price. If the price drops and the dividend stays flat, the yield printed goes up. So a very high yield often means the market marked the shares down, and the screen hasn't caught up.
What sits underneath it: a mortgage REIT borrows money short term and buys mortgages or mortgage-backed securities, which are bonds made of pooled home or commercial loans. It keeps the difference between what it pays to borrow and what the mortgages pay. That difference is the spread. On agency mortgage bonds, the ones backed by Fannie Mae or Freddie Mac, the spread might be 1.5 percentage points. That's thin, so the company borrows several dollars for every dollar of its own equity to turn it into a double digit return on equity. That borrowed money is where the risk lives.
The piece people miss is book value. Book value per share is the company's assets minus its debts, divided by shares. When rates or spreads move against the portfolio, book value falls, and the share price usually follows. You can collect 13% in cash and still be behind if book value dropped 15% over the same stretch. So the number to track alongside the dividend is book value per share, quarter by quarter, which every one of these publishes.
Total return is dividends plus the change in book value. Judge the holding on that, not on the yield column.