Herlock Sholmes: Yes, that is right. I agree the instructions are a bit vague.

One way to think of it is that in triple dice poker, the bonus is calculated by the score that you get if you had scored three of each number, and in triple dice poker the bonus is calculated as if you had scored four of each number.

If you think of it that way, and you realize that you only got three 6's in 6D, then you need to make up that extra 6 somewhere else, for example by getting five 5's and five 1's, or five 4's and five 2's.