in one of the four image points, 2,3 or every sprite could spawn in one single image point, it's random. But that is not the point, the thing is making them spawn in a random quantity.
Use a for.
Im using 2 variables to be easier to understand, but its not necessary.
Var min_enemies=1
Var max_enemies=7
For 1 to int(random(min_enemies,max_enemies+1))
Create sprite enemy at X,Y