Markus,
I agree with the beginning of your calculation.
I just don't agree with the end, but maybe time in Sweden is not the same than in France, due to arctic circle or midnight sun ! (please do not take it as an offense, it's pure humour
) !
One hour = 60 minutes = 60x60 (3600) seconds , and not 1440 which is the value you appear to have used !
Which means you should download your 4 GB in 16978 / 3600 = 4,71 hours - a bit less than 5 hours
Oh, and btw, you could have had the same result quickly with this simple but efficient calculator :
http://www.numion.com/calculators/time.html
Besides of all that, we are talking about theory here. Effectively, if you use a 3G data connection, I imagine you might have a very variable download rate, and probably some deconnexions
Regards
!