Reversal and segment clearing account

Hi,

We reversed one document at that time system is posting to wrong profit center. but in initial document it was posted to right profit center. at the time of revesal only why it was posted to wrong profit center.

and in this reversal segment clearing account is having 2 line items in debit and credit.

why segment clearing account came in to picture at the time of reversal.

guide me

sateesh