Dear Itika,
First of all, u r not sure that actually u have made a mistake or not, so point in worrying.....:)
(Infuture keep zerox copies of such things before submitting to the institute)
Secondly, even if we assume that u have not encircled the Certificate No., then also nothing can be done now.....so no point in worrying in this case also......:))
So, In short morale of d story is "Dont worry, be happy"
Ok now serious,
even u have not encircled the certificate No., then agree that system will not process that form but friend utlimately some person will look at it no that y this form is not being processed by the system & he will mark necessary circles (since it is written there)
Dont worry, this will not be an issue.............Just try to check ur roll no. as & when it appears on the website...
One of my friend told me that even in some cases where there are serious descripencies, Institue allows student to appear in the exams only thing is announcement of result gets delayed subject to the clarification by the students.