Vendor confirmations in PO

Hello,

I have a simple question regarding Vendor confirmations.

I have setup vendor confirmations for acknowledgment "AB" only for my PO...i have a delivery date of assume 20 Nov 2010....so when vendor sends me order confirmation that he will send me goods not on 20 but on 22nd NOV 2010....so now through EDI transmission the vendor sends confirmation which goes and update my PO confirmations tab....vendor comes back again on 20th Nov and sends another confirmation that....he sends a new confirmation that goods will be on 25th Nov 2010....now will the system update the same line in the confirmations or it will create a new line in the confirmations tab?

Regards,

Andy