How do you prioritize optimization of the mobile site for browser versions or screen resolutions:
Prioritize the site with the highest conversion rates
Optimize all at the same time
Look for the oldest version of your site
Look for the highest number of sessions and lowest conversion rates (or highest bounce rates)
Explanation:
Understand if users’ experience differs on different browsers or screen resolutions: Prioritize optimization of the mobile site for browser versions or screen resolutions with the highest number of sessions and lowest conversion rates (or highest bounce rates). For example, if you observe low conversion rates for some browser versions or screen resolutions, make sure your CTA buttons stay in natural (easy-to-reach) areas and make sure they are functioning.
Read more here: https://support.google.com/partners/answer/7336696