First of all, the person you originally replied to didn't only include the people that died, he/she also included those that were wounded or were in the city center at the time of the bombing (the city center part on its own brings up by a lot the number of people directly affected by it).
Second, how is having 254 people as your acquaintances an absurdly large number? They don't have to necessarily be friends, you know.
Ignoring all that, though, as has been mentioned, Norway is a fairly tiny country (by population), 77 people dying in Norway from a terrorist attack is equivalent to 2310 people dying in the US from the same thing, which is fairly close to 9/11. And Americans in this thread count that as one of the biggest shocks of the last decade. So yeah, let Norwegians have their day.