File size fluctuation

Hello,

I’m using the filestat plugin to monitor the size of my Apache access log. How do I configure Grafana to send out an alert if there is a +5MB or -5MB difference noticed? I’m sending the file size stats every 10 seconds from the Apache server.

For example if my avg file size is staying at around 20Mb but then it either goes up by 5Mbs or goes down by 5Mbs then how do I configure Grafana to alert on that ±5 Mb change?

Thank you!