prodState is a variable that will hold the production state value for the device generating the event. Production state 300 is what you will get from any device in 'maintenance' mode, I think 1000 is what you get for normal 'production' state.
So basically the transform will look at any incoming event (even the 'clear' events, or in my case 'traps') and if they are from a device in 'maintenance' mode, it will drop it.
Manuel