Max-age for anonymous users

Hi,

How do I verify if anonymous user is served with cache files. I use simple cache.

This is the http response header I get when not logged in:

cache-control:max-age=3, must-revalidate
cf-ray:3c8797d19bed17c2-SIN
content-encoding:br
content-type:text/html; charset=UTF-8
date:Tue, 05 Dec 2017 14:11:11 GMT
server:cloudflare-nginx
set-cookie:__cfduid=df8da2e3925c56f5a466d02724ebb30b21512483069; expires=Wed, 05-Dec-18 14:11:09 GMT; path=/; domain=.kpopexplorer.net; HttpOnly
status:200
vary:Accept-Encoding,Cookie
x-mod-pagespeed:1.12.34.2-0

Why “max-age” is only 3?

Regards,