Hello, hope someone can clear this up for me....I cant get my head round the ww points for sugar....

I weighed out 3 teaspoons full [ok,very full!], and it came in at 20g. So, by the booklet it is 2points. [5g = 0.5 so 20g = 2]
But, by the ww calculator 100g = 5.5points so 20g is 1.1points.Obviously it should be rounded up to 1.5.
So I am very confused! Is it the 2 points according to the booklet, or the 1.5 points according to the calculator? Really hope someone can help!