[jonathan_h]

TL;DR: A minimum score of 1 messes with their formula. OP should consider changing it.

Looking at the page's <script>, I think it's because they set the minimum score to 1 rather than 0.

In addition, for three of the questions, a high score is seen as a negative rather than a positive (e.g. a high score in "development effort" likely means "a lot of effort"), so behind the hood they invert those scores by doing (10 - score).

The problem is then that positive questions have a range from 1 to 10, and negative questions have a range from 0 to 9, and the means you have a minimum score of 3 and a max of 57, rather than 0 and 60.

For a more flowery answer: A developer never deals in absolutes :)