Hello, 

There should be no problem regarding the format until the verification officer is very strict with the rules. Most of the people there are very helpful and will not block your seat for the mere reason of your document not matching with the format. Yet for safety reasons, you should try to get it signed in the recommended format. You just need to take the printout of suggested format and get it stamped on the basis of your already issued certificate. It is better to be safe in these procedures as your one-year and a seat in IIT is at risk.