Hello !
Don't worry. It is a totally wrong concept.
12 percentage really matters but there are companies out there that focus on skills of the individual rather than 12 percentage.
Just focus on your course develop pure skills.
Try to build an Excellent resume. Participate in symposium participate in coding competition. And never stop learning.
Getting a job is just one step towards a good future but maintaining the job takes real skills.
Hope this helps.

Dear Manoj,

If you make it to the top IIT's Computer Science branch then none of your previous marks matters. In fact, most of the recruiters will not even be affected by your graduation marks. Do not worry about your past, if you are preparing for GATE then do your best.

Some of my seniors even have backlogs in their graduation but now they are in top companies.

Hope this helps.

Thank You.