To get to the Tab's factory menu, open calculator application on your Galaxy Tab and type
On android 3.X version (+32286798378+           left bracket, plus, 3,2,2,8,6,7,9,8,3,7,8, plus
On android 4.X version (+30012012732+           left bracket, plus, 3,0,0,1,2,0,1,2,7,3,2, plus

Android 4.X example: