I chose 900W in the configuration with default fan and temp settings and it auto tuned my S9i to 825W at 11.9TH. That's 69.3 W/TH
Another S9i I chose 800W with default fan and temp settings and it auto tuned to 723W at 10.4TH. That's 69.5W/TH. It always ends up with a watt reading lower than what you choose on the configuration page.
Can you give us some details, in method of measuring, which kind of mains voltage, and what exact S9 model/speed you used to achieve this? Its quite impressive to have under 70 W/TH actually

I measured the watts at the wall with a standard watt meter. The miner is on a 240V line. Model is S9i 14TH.