Paper loss. It's a sort of debt they have on bonds that is tied to their valuation. Because their valuation has grown significantly, so has their debt. It's standard accounting process to put that debt as a "loss", even though they're not paying anything.

Think of it this way. It's as if a public company gives you a certain amount in RSUs that won't vest for a while. A year later, the company is worth 10x more. So they list the increased value of the RSUs they owe you as a loss.

In reality, the fact that this "debt" has ballooned so much is a positive sign - the valuation is high (it's a separate issue whether that valuation is realistic).

Their "real" losses are about $8B.