That is true for deep work like:
- solving mathematical problems
- coding non-trivial stuff
- teaching non-trival stuff
The challange is shallow work e.g.
- replying to emails
- meetings
- scheduling meetings
And than there is no-work:
- checking your phone
- lunch
- walking and chatting before the next meeting
Shallow and no-work can easily eat anywhere between 20 and infinity :)
Besides - doing meetings well is not shallow work at all; scheduling is a pain etc and emails are written better when people aren't tired.
That is true for deep work like:
- solving mathematical problems
- coding non-trivial stuff
- teaching non-trival stuff
The challange is shallow work e.g.
- replying to emails
- meetings
- scheduling meetings
And than there is no-work:
- checking your phone
- lunch
- walking and chatting before the next meeting
Shallow and no-work can easily eat anywhere between 20 and infinity :)