Can anyone explain this score process easily?

Just subtract the score from 8 for questions 2, 4, 6, 8, 10. Then average out the pairs of answers relevant to each trait.

For example, Extraversion is scored from question 1 and question 6, and both questions are initially scored 1 to 7 for agreement.

Question 1 "Extraverted, enthusiastic" 

Question 6 "Reserved, quiet"

Question 6 is clearly the reverse aspect of extroversion and so effectively we want to score the answer 7 to 1 instead of 1 to 7. And mathematically we do that by subtracting the original score from 8, eg original score of 3 is a reverse score of 5.

So if the original answers were Q1 = 7, Q6R = 3, 

this would give us 

Q1 = 7, Q6 = 5, 

Then (7 + 5)/2 = 6 for extraversion