After success of previous edition of the 'Grand Slam' counter: hltv.org/forums/threads/2751977/grand-sl..
which made it to official ESL twitch and YT transmission of the event and was discussed by the panel I'm back to give you the answer you were all waiting for. xD
In a match FaZe vs Forze 'Grand Slam' was mentioned in total of 15 rounds. That's 19% of all of them.
Nobody predicted correct number or percentage.
Closest were allahiyedim and best_igl_NA predicting 13 rounds.
Type below number of rounds and % of rounds you think 'Grand Slam' will be mentioned in NaVi vs FaZe match.