During the admission procedure, the candidate is judged upon the weightage of their GATE score, GD or PI, and their academic credentials.
Considering your score being lower than usual, then it is the GD and PI that will play a pivotal role in your further selection. It also partially depends upon your communications skills because, only last time, NITIE offered management courses to a few handful of students based on how fluent they were with their communication skills.
NITIE Mumbai does not often divulge the criteria they usually follow for shortlisting students or finalizing candidates. It is best to acquire the best GATE scores.