Add documentation for https://github.com/pi-hole/FTL/pull/1295

Signed-off-by: DL6ER <dl6er@dl6er.de>

docs/ftldns/telnet-api.md

@@ -161,6 +161,12 @@ Connect via e.g. `telnet 127.0.0.1 4711` or use `echo ">command" | nc 127.0.0.1
     53
     ```
 
+- `>maxlogage`: Get timespan of the statistics shown on the dashboard
+
+    ```text
+    86400
+    ```
+
 Note that the port can also be `0` if someone decides to disable the DNS server part of Pi-hole
 
 {!abbreviations.md!}