Section 11 presents calculations of the probability of double spending (P) given an attacker relative hash rate *q* and a network block count *z*.

[![Calculations][1]][1]

I'm not sure how to interpret a situation in which *z* = 0. The results say that that P = 1, regardless of attacker hash rate.

Does *z* = 0 mean that a transaction hasn't yet been confirmed, or that it has been confirmed but its block hasn't yet been extended?

If the latter, this would imply an attacker with zero hash rate can double spend with 100% success. It would also conflict with this statement:

> *The recipient waits until the transaction has been added to a block and z blocks have been linked after it.* He doesn't know the exact amount of progress the attacker has made, but assuming the honest blocks took the average expected time per block, the attacker's potential progress will be a Poisson distribution with expected value... [my emphasis]

What am I missing?


  [1]: https://i.sstatic.net/Ta1wp.png