Randomseed, is normaly used to determine the random number sequency.
It works that way in other languages. I think the idea is, computers cant create true sequences of random numbers. So you use the date\time as the seed, to create what looks like a random sequence. But keep reseting your clock, you would get the same sequence all the time.
So all it should mean is, you get the same wind direction every time you play the mission. It might help, as you could use trial and error to make sure they eject at a position that allows them to land safely.