if you are growing a tiny clowntrigger , if you are lucky and got a healthy fish (as in tiny size no more 1 in 10 survive more than one year ) it will grow to 10 to 15 inches ...after a long time ( I got one tiny to 6 inches in 8 years) and considering a good diet and spaciuous tank...
If you got a bigger trigger ( more than 4 inches) after the first year, it will grow a inch every year but will stop at 8 to 10 inches size (I got one from 3 to 9 inches in 10 years in one of my maintence customer tanks.
hope to help you...