What does this report Column mean?

FreePBX 2.3.1.3 TB 2.4

Under the Reports Tab - Call Detail Records there is a nice Graphic of calls by Day. Everything is self explanatory except the last Column labeled “ACT”

Can anyone enlighten me on what it’s based on, and/or calculated ?

JMS…

Average Call Time

An yes, my brain reengaged a couple of days latter and this clicked …