Currently, NIT Calicut follows a hybrid grading system. While some subjects follow absolute grading, some subjects follow relative grading. It depends on the subject and the professor teaching the particular subject. However, a subject can have only one kind of grading system.
The relative grading system followed by NIT Calicut is different from that followed at the IITs. It has nothing to do with the percentiles. The marks obtained by the top 5% - 10% of the students are given the top grade, i.e. S. All other students are given grades lower than them accordingly.