@tence
Hello mr Tence also Paladin and thank you for contacting me with your issue. I can see that you are telling the truth, as both your screenshot and the armory I checked show the number 4105. However, to properly rank up every single person that signs up I decided to use a program to do it for me, so I don't have to check a hundred armories every time and rank them manually.
If I want a program to check how many points one has, I have to use the Official Battle.net API (tm). Those show me, that you have 3755 points:
This is of course incorrect, so I check another api call I can make, which resolves to tell me you indeed have 
18545 points. I can only assume that this is your whole account's points.
So, even though I know that everyone's achievement points are fucked up, including mine, I'm out of ideas on how to fix it, because Blizzard gives me wrong numbers :/
So far I've seen that everyone gets less, so even if everyone loses, it's still pretty much balanced. Maybe they don't count some of the achievements on their end of things? I have no idea.