Calculating yearly salary into weekly salary?

I know this seems like an obvious answer b/c there are 52 weeks in a year, but my friends are telling me that $55,000 per year works out to be $1145 per week or $2290 bi-weekly. They are using this method of 48 weeks(12x4 weeks) to get their answer. I am assuming that their pay stubs are saying that they make $1145 bi-weekly amount. So I am confused as to why their yearly salary that they signed off on is $55,000 and not $59,540. I am so confused and beginning to doubt myself. This is before taxes of course. I can't help but think that they are mistaken and THINK that they are making more than they actually are and did not check their pay stubs thoroughly b/c it is direct deposit . My dilemma is that I have been offered a salary in the "per annum" form at the same company as my friends. I was insulted by the yearly salary that they offered b/c I felt it too low, now I have doubts as to whether or not I am calculating things right, thus making my negotiations confusing since my salary at my current job is weekly. Perhaps I should just ask for the contract to be written as a weekly salary? Would it be frowned upon to ask for a weekly salary contract? Is there something to my friends calculations that I am overlooking, and perhaps this is how the company figures it out?