Alerts Statistics

I need help to interpret Alert Statistics Graph. I need to know when and how long one device was down.

For example, in the attached graph, I don’t know what mean the number 60 in Y axis and in X axis no legend appears.
Can I create availability report for a device? how?

Thanks in advance.!!

==================================== Component | Version --------- | ------- LibreNMS | 1.52-54-g1a60c44eb DB Schema | 2019_05_30_225937_device_groups_rewrite (135) PHP | 7.2.19-0ubuntu0.18.04.1 MySQL | 10.1.40-MariaDB-0ubuntu0.18.04.1 RRDTool | 1.7.0 SNMP | NET-SNMP 5.7.3 ====================================

[OK] Composer Version: 1.8.6
[OK] Dependencies up-to-date.
[OK] Database connection successful
[OK] Database schema correct

A. Check event log
B. Check uptime graph