To understand the full value of mobile, you must take into account:
- Mobile conversions
- Utilization of mobile ad formats, extensions, app and mobile site design best practices
- App downloads, calls, store visits, cross device conversion, mobile conversions
- Cross device and mobile conversions
Measure the Full Value of Mobile by taking into account the different conversions that a mobile user could generate for your business (e.g., converted clicks on your site, cross-device conversions, calls as conversions, website call conversions, app downloads and in-app conversions). Because Onsite conversions are just one part of a mobile user’s potential experience with your brand.
Read more here: https://support.google.com/adwords/answer/6167155?hl=en