The average session of my site is in 29 seconds. However, I have found that what is affecting this metric (which should be at least 1 minute) is the simple fact that the internal links on my AMP page are redirecting to the non-AMP page. Although the code of the analytcs is the same I do not know why google resumes the count when the user is redirected to the non-amp page.
It's a relevant subject because google considers visiting time as an important factor for SEO, but I do not understand why it resumes counting when the user exits the page amp and goes to the amp.
Has anyone noticed this problem yet?