Some of the events in the score are supposed to be syncronised from signals from the conductor or sound signals from the other performers.
Other events are more fluctuous in time and can be performed whenever the performer feels like it within the actual part of the piece.
The score was a notation of the compositional process leading up to the start of the rehearsals and it was acted upon freely.
It was a sort of guiding map, but still with terretories of undiscovered places. A starting place for improvisation.