I would think about re-organizing your code according to Object Oriented principles... chiefly modularity.
i.e.
Make a function that spawns a boss bullet a specific number of times. You can randomly generate the angle and image spawn point within certain bounds (it looks like your angle in bounded 230-310 deg). Then you can simply call that function and input a specific number of times that you want the boss to fire.
In this function, use trigger once and a for loop with an input parameter for the loop number, something like:
local variable randomImagePoint = -1;
local variable randomAngle = -1;
Function bossSuperAttack (Number_Of_Shots)
trigger once
for loopindex: 0 :: Number_Of_Shots
randomImagePoint = round(random(6));
randomAngle = round(random(81)) + 230;
Spawn BossFinalWeapon on Layer 4 (image point randomImagePoint);
Set angle to randomAngle;
Wait 1 sec;
[/code:297gb12x]
Then when you want the boss to fire four shots (on a certain condition) you simply call bossSuperAttack(4).
If you don't want the attack to come from different points each firing, simply move the random assignment up one level to the function, rather than inside the loop (like the above shows).