Does a husband's utterance, "And you are divorced from me on that," count as a second divorce? And is the 'ibra' (release from marital obligations) valid after giving the wife her full deferred dowry and maintenance? And is the third divorce, issued out of ignorance after the divorce by 'ibra', to be counted?

If you divorced your wife with the first pronouncement of divorce (talaq (definition)), without stipulating ibra' (release from marital obligations) or compensation, then your divorce is revocable. What happened at the ma'dhun (authorized divorce official) afterwards is of no consequence, because it occurred after the first divorce had taken effect. For a divorce of ibra' to be valid, there must be a prior agreement on ibra' in exchange for divorce. If the pronouncement of divorce at the ma'dhun was intended as notification of the first divorce, and not to create a new divorce, then no further divorce occurs thereby. However, if you explicitly pronounced divorce again a month after the first divorce, and this occurred during the wife's iddah (definition) (waiting period), then it is effective, even if you were unaware of the ruling.