Hello aspirant.

Gm means general merit and GMK means general merit with kannada medium reservation .

For kannada medium quota , a student must have studied in kannada medium from class 1 to class 10 , and you must get certificate . Total there is 5% reservation in government quota seats .

For more information refer 

https://www.google.com/amp/s/engineering.careers360.com/articles/kcet-reservation-criteria/amp

All the best.