A PABX can report multiple calls on the same extension, but different lines, if a "Cradle Bounce" occurs.
This is when you press down the hook with your finger, to end a call and then start another call.
The PABX can keep recording the line as active, since the call is treated as a call that is on hold.
Once the extension then ends the last call,
all other calls still on hold for that extension will end at the same time.
This is why it would seem that more than one call would end in the same minute although they are not the same length, or even to the same number.
This will easily be noticed as the same number occurring multiple times or a number misdialed.
Thank you to Donovan and Privey
(Spelling:)
Also See: Conference calls and Call forwarding OR Duplicate times on same extension