Cacluation of three days entrance fee in JiuHuaShan

The entrance fee to JiuHuaShan is CNY190 valid for three days.
How is the days calculated?

1. We estimate to arrive JiuhuaShan on 13th Oct. around noon.
2. Must we leave on the 15th Oct (3 days) or
3. We can leave on 16th at noon (72 hours)

thanks and regards