[ry0ohki]

It's an existing investor solidifying a deal. Kind of like if you bought a stock at $40, and now it's down to $20. You look at the company and think "OK, maybe our initial investment was at a high valuation, but I think think there is a good chance we can at least get our initial money back if we keep you afloat for a while", so you buy more stock at $20, making your overall cost basis lower. Without that investment you are guaranteed to lose your money, but this way you are doubling down on your original bet, and giving the company some more runway to potentially at least break even on the exit.