The CDR columns billsec and duration shows the values in neg

I am wonder suddenly my CDR database of Asterisk are showing the billsec & duration in negative sign like -43060 and -43059. I am confuse what does this mean I check the recording file of the same call it is of duration 2 min and 11 sec. But why in mysql it is showing such numbers.
Can anyone explain me please here.
Thanks in Advance.

These are calculated from the start, answer and end times. Find out why these are wrong.

Note that you need Call Event Logging and Asterisk 1.8, if you want to do accounting of complex calls.