Roydsey,
My advice would be to go back to Tutorial 4 and make sure you did all of the enemy ship script right. That is where you will get delays between ships.
Voniche,
Firstly, _y = Math.random()*200+50; is equal to between 50 and 250.
The reason these both work is that the *200 is multiplying 200 by 0-1 and then adding 50 to the total making it a minimum of 50 and a maximum of 250, and for the other one *5 is multiplying 5 by 0-1 and then adding 5 to the sum making a minimum of 5 and a max of 10.
If you follow the directions of the tutorial your * (in this case 5 and 200) will always be multiplyed by 0 or 1, then the + (5 and 50) is added to the total of the multiplication to set a limit for the variables.
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