In those pages:
https://doc.nuxeo.com/910/nxdoc/upgrade-from-lts-2015-to-lts-2016/#nuxeo-studio-application-definition
https://doc.nuxeo.com/910/nxdoc/upgrade-from-lts-2016-to-lts-2017/#nuxeo-studio-application-definition
Both links named How to Update the Version of Your Target Platform in Studio point to the Nuxeo upgrade page and not the Studio related one.
The proper target link should be:
https://doc.nuxeo.com/studio/update-the-version-of-your-target-platform/