I believe it's more a reference to the allowed civilian casualty rate. If they're allowed to kill 10 or more civilians per bombing of a suspected target, then even if they're 100% accurate in targeting their suspects, 90%+ of the people killed will be civilians.
The article says 10% errors, is it possible you’ve transposed it?
10% still seems too high, but 90% would be absolutely nuts.
I believe it's more a reference to the allowed civilian casualty rate. If they're allowed to kill 10 or more civilians per bombing of a suspected target, then even if they're 100% accurate in targeting their suspects, 90%+ of the people killed will be civilians.