But random number could result in 1548415456
No it doesn't, unless you use
random 1548415456.
And you can't even use it like that with a position since position is in three dimentions: [x,y,z]. It returns an array of values, such as [67543.1,8378.23,0.23476]. When you're dealing with arrays each element in it has to be dealt with individually. Element is an entry in the array separated by comma (or what ever , is called).
The first elements index number is 0, the second is 1, and so on.
The format of the random command is
random <number>, so if you set for example
random 5 it will return a random number anywhere on or between 0 and 5.
I'm assuming since it's a arty script you would want to have a random position around the given position, within a random diameter. For that you need some trigonometry.
So try something like this:
; random diamater between 0 and 150 meters
_randDia = random 150
; random direction
_randDir = random 360
; create shell within the random diameter between 50 and 100 meters into the air
_shell = "Shell125" createVehicle [(getPos _pos select 0)+_randDia*sin(_randDir),(getPos _pos select 1)+_randDia*cos(_randDir),50+(random 50)]
Note that I'm a complete math retard so the trig part maybe completely wrong