Not exactly one third. For example if total word count is 300 then precis can be from 80 to 120. And yes you are right regarding precis of 2021 that it was very difficult to make it upto one third because there was very less substance related to ideas that we had to put in precis.

__________________
''Sufficient for us is Allah , and He is the best Disposer of affairs" Al-Quran