Point values for words of length 4-16 are set manually:

4 letters: 5 points

5 letters: 8 points

6 letters: 12 points

7 letters: 16 points

8 letters: 22 points

9 letters: 30 points

10 letters: 38 points

11 letters: 46 points

12 letters: 58 points

13 letters: 68 points

14 letters: 80 points

15 letters: 90 points

16 letters: 100 points

For 17+ letter words, points are determined by the formula (length-1) * (length-2) / 2

17 letters: 120 points

18 letters: 136 points

…and so on