Forgot to make the entries in the column 6.6 of vat 100

Yes., u can file revised returns.

For ur reference: In the state of KARNATAKA

"A Dealer is now permitted to file ‘Revised Return’ for a month only within 1 month from the date of original filing of Return. e.g., Return for the month of April is filed on 20th May. The Revised Return should be filed within 20th June.
• If the dealer desires to file a Revised Return after the above date, then he has to get permission of LVO or VSO. With the above permission, he can file the Revised Return within 6 months."