I have split "Start Part" and "repeating part" to two Sequences.
Then we need to tell RailClone to use starting part only once,- first floor.
So we plug both sequences- start, and repeating to Selector Node. And tell it to use FirstFloor only once,- only on first floor.
This is done with arithmetic Equation which is wired to Index input.
That is pretty much it. If You want some step explained in more details, please spicy which.