This page is . It is not a New Relic domain and holds no New Relic certificate. Steps 1 to 6 run in your browser, using only the session cookie your browser already has for New Relic. Step 7 runs on this page's own server, to show the stolen key still works with no cookie and no browser.
Your account ID is the account= value in any one.newrelic.com URL, or under Administration → Access management → Accounts.