Does Richard Davidson mislead us with numbers how long to meditate daily?

Matthieu Ricard said he meditates 20 min. daily, Cody Rall MD with Techforpsych said he meditates 20 min daily, Yongey Mingyur Rinpoche said he mediates one hour a day. Is this because they listened to what Richard J. Davidson writes in Altered Traits»: But world renowned leaders in meditation give completely different numbers. at 4:38 …