I still don't understand what these "probabilities" illustrate? Either a transaction can be traced or it cannot. What exactly are the probabilities of?
If you compromise a masternode and spy on it's activity, you can theoretically start to piece together all the required information to trace a Darksend transaction back to a user's wallet. Since nodes are selected randomly for Darksend, you would need to compromise the correct nodes to do so. These are the probabilities of you having compromised the correct nodes and therefore being able to decode the transaction.
Okay that makes sense. Thank you.