Received a 4549 and 886 A notice from IRS today, now what should i do

over 30 days ago i received a letter of review and request for supporting documents. I faxed 39 pages of information in and on March 6 . today in the mail i received a notice  4549 income tax examination changes, and 886-A explanation of items. I dont understand any of it. i was sent my with holdings feb 27th and now the notice said i owe $218. why did they send me my withholdings and then turn around and want $200 of it back?