What exactly is INTERVAL 1 HOUR checking? MariaDB 10.1.x

Let's say I have a query like: 

select FOO from db.BLAH where STAMPFOO &gt; NOW() - INTERVAL 1 HOUR

If I run that query at 12:15 PM, will I only get records that have a date value greater than 11:15 AM?  Or greater than 11:00 AM?
Since the WHERE clause says NOW(), the expression STAMPFOO &gt; NOW() - INTERVAL 1 HOUR makes this a dynamic query. It will return all records whose timestamp is greater than one hour ago, down to the very second.

If you run this at 2017-02-02 12:15:27, your query will return all FOO values  from 2017-02-02 11:15:27.