You should discharge to 4-5% and let it cool down. Charge it back to 100% may be after an hour of cooling time. Idea is that battery should not be charged in hot conditions else it's internal temp may cross its limits.
How are you discharging? If you are using drone to discharge without props, I suggest to keep a cooling fan to cool your drone. Drones electronics needs air to cool and that it gets during flying. But when you are using it to discharge batteries without props, electronics will not get enough cooling.
Deep discharge after 20 cycles was proposed by DJI. In fact I do something different. Every time I use charged battery, I check its capacity and if the capacity shown in DJI Go App is lower by say 10-12% of its rated capacity, I take it up for deep cycling. You will see that it recovers its capacity to almost full rated capacity. As the batteries goes old, you will not be able to get back to full capacity but that's ok. You at least know how batteries are getting old and you need new ones. For your information, if you maintain batteries well, you can easily get 200 flights with each battery if not more. Enjoy.
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