Where nb_uniq_visitors?

General questions
1

there is no “nb_uniq_visitors” in my api json return, why ? i can see on the demo.piwik.org is ok.

http://demo.piwik.org/?module=API&method=Actions.getPageTitles&idSite=7&period=day&date=today&format=xml&token_auth=anonymous

[attachment 1701 1.jpg]

2

See: How to - Analytics Platform - Matomo