On 'Start of layout' happens 1 time and in the time of 1 tick.
A 'for' loop happens in the time of 1 tick.
So, the system will once and only once visit that "every second" condition.
To make that 'every second' work, the system needs every tick access to it, the system will look if its time to fire its events, if not it moves on.
You need two global variables.'lvl2Rand' (=zero) and 'Counter' (=zero)
In that On Start of layout event, you can set lvl2Random as you did.
Outside that event, and as a top event :
On every (1) second.
_____sub event : System compare 2 values ... 'Counter' ... is < ... 'lvl2Rand'.
_____Action .. spawn 1 object
_____action .. add 1 to 'Counter'
Now the systems eye will look into that condtion 'every second' each tick. When its time (1 second) if will fire the sub events. When it is not time yet, it will skip that event. That is how it does that Every x seconds.