I didn't catch that. I believe it should have been $20 also, but I've seen various explanations out there about what the final price should be. All are in agreement that if they take in multiple bid levels everyone gets the same price and they will get the higher and not the lower pps.
This definition states that if not enough shares are tendered then it would be the max price. I wonder if the author from the above was thinking about that scenario? I don't think the max price is going to matter to WNTR because the phrase "up to 1 Billion" probably excludes them from ever having to pay that out if not enough shares were tendered.