Just bought 3 tickets for Huddersfield game

i thought we got 20 points per ticket giving me 60 points but on my account it shows that I got 20 points for the lot

Is that right ?

Yes.
As I understand it, you'll only get one set of points for the whole purchase made against your OWN membership number but if you're buying for other members too, who are tied with your account using "friends and family" and you select a ticket for EACH person during purchase, then you'll all get points, saving you all having to buy individually in order to get your points.