Why don’t you just count the number of enemies instead of use of a variable.
Use Advanced-> Compare Two numbers
Count(FrontEnemy) > 0 That means at least 1 enemy is in the level.
Count(FrontEnemy) <= 0 That means there is no Frontenemy object in the level.
With this you only need to set a timer that starts one time and keeps running until the number of enemies that you want to spawn.
Any Action with Trigger Once or most probably at the Begin of the scene
If the timer “StartSpawn” is greater than 3 sec
Count(FrontEnemy) < 10
Action: Create enemy…
Edit: I think in your events you’re resetting Diana timer in the repeat so that only happen one time