I think you're all missing the point discussing calculations, instead of analyzing the shown events logically. Spooner and the girl were on the same level in the water. She was still alive and fighting when the robot jumped on Spooner's car. If the robot decided it couldn't save both based on calculations of chances of survival, well, you now have the reason why that robot line was replaced by Sonny's new generation. The general feeling we get during the movie is that they're not all that effective. Spooner's anger comes from the fact they covered the robot's failure with statistics, and his anger in turn began to encompass all robots. A subtle theme in the movie is how corporations treat human life as unreliable objects, numbers and factors to be replaced by machines robots, much like Calvin was acting towards Spooner at the start. It's not a message against robots, but against their creators' attitude and the common people who trust blindly on them, like Da Chief and Gigi.
Spooner: What makes your robots so perfect? What makes them so much... goddamn better than human beings?