In this post you will understand how ETS converts rubric scores to scaled scores in the Speaking section.
The Speaking section contains six questions, and each one is scored from 0 to 4 points without decimal values.
For example, you can obtain the following set of results [4,4,3,3,3,3]. Then, they calculate the average of the results (sum of the the six scores divided by number of elements):
(4+4+3+3+3+3) / 6 = 20 / 6 = 3.33
and the outcome (3.33) is converted to a 30 points scale. See the following table:
To learn which are the scoring standards for each question check this link: Speaking standards