600 is the minimum time in seconds between two reports. It means - do not send any battery level updates if less than 10 minutes have passed since the last report. Even if the battery level drops rapidly from 100% to 1% - keep it silent, until the 10 minutes interval from the last report is elapsed. Do not report more frequently than 10 minutes.
21600 is the time interval in seconds in which the device should report the battery status, even if there is no change. I.e. - send a battery report every 6 hours, even if there is no change.
1 (percent) is the minimum battery level change that will trigger an automatic report if the minimum reporting period (600 seconds have elapsed since the previous report) has passed.
The meanings of the 'minimum reporting interval' and the 'maximum reporting interval' are often misunderstood, which results in temperature and humidity sensors sending updates very rarely, even if the temperature rises by 50 degrees or humidity increases to 99% - the sensors keep radio-silence, because of the wrongly set 'minimum reporting interval'.