Call Statistics - What do "calls" field represent

[itsystems.ie]

The new call logs & the Call Statistics report. It shows
Number, Kind, Calls, Answ.Calls, Not Answ Calls, Total Time, Ringing Time, Talking Time

We hold a manual log for outgoing calls for Ext. 200. The Call Log shows
Calls = 52
Answ Calls = 31
Not Answ Calls = 21

We know from the manual log that only 31 outgoing calls were made from this extension. Why then is Calls = 50

Can someone please explain.
Thanks