PGCET counselling started with mock round for students to get familiar with the admission process.in first round of seat allotment candidates who score high in GATE/PGCET a merit list is prepared according which seat is alloted to them they have choice if they accept seat and withdraw from counselling or they reject seat and go with the second round in which they avail the facility of modify their choice.so yes you can add/ delete your choice in further rounds within a time period.

All the best!!!