Billing Number buffering by 2

Hi guru's

in my scrap sales invoice iam getting buffer by 2 .. like 2, 4, 6, and 8.. .. i checkd SNUM/SNRO, iam difficult to find the billing Numebr object.. and also if i select the any object i seen the main memory bufferning checked and in display mode.. ..

wat i ahve to do.. tell me the process.. step by step.. reward full ..

Ramki