A single tick represents one hundred nanoseconds or one ten-millionth of a second. FROM MSDN.
So 28 000 000 000 * 1/10 000 000 = 2 800 sec. 2 800 sec /60 = 46.6666min
Or you can do it programmaticly with TimeSpan:
static void Main()
{
TimeSpan ts = TimeSpan.FromTicks(28000000000);
double minutesFromTs = ts.TotalMinutes;
Console.WriteLine(minutesFromTs);
Console.Read();
}
Both give me 46 min and not 480 min...