Hatarat Nedairm

I have been told that on Erev Rosh Hashana, The Hatarat Nedairm anullls vows of the coming year, and that this can be relied upon. Why should it matter if a specific Neder was made as I saw an answer on this site that this is not enough? Also, am I right in saying If someone wrote an e-mail about ie. learning, and, and when re-read before sending, noticed a mistake (saying that one cant learn a topic alone but sadly can guarantee to learn with someone, where one should have typed cannot) in the email and corrected this, this is not a Neder as it was a typing error?

On Erev Rosh Hashana [and Erev Yom Kipur] we do two things in regard to Nedarim – vows. First we annul the vows we have mistakenly made during the past year, which is the classic Hatarat Nedarim – annulment of vows. In addition we proclaim that all vows we will make will be annulled and void from now onwards. The Mishnah Brurah [619; 2] comments that this proclamation is only valid for vows made in case one does not remember this previous proclamation, if however he does remember it at the time – the vow is valid and requires a proper annulment to erase it. There are other opinions on how it works and therefore even in the case when a person did not remember his Erev Rosh Hashana statement and later on made a vow, he will require an annulment by a competent rabbi. Vows are only valid if the mind and mouth meet, i.e. if one said something he did not intend to, the words do not count as a vow. [see Kitzur SA 67; 6]