There might be more to that than the mistake Nimoy made. It might result in an opportunity to hint at something going on that while not making immediate sense to our 20th century ears could have meaning to a technology or physics we don't yet understand. For example, if he is saying "one to the fourth" and you read it as "one to the 1/4" you end up with factors of 1,-1,i, -i. That is more interesting than just one - particularly the imaginary numbers.
http://forums.xkcd.com/viewtopic.php?f=17&t=86266
Interestingly, the actual scripted line in "Court Martial" (it's Kirk's line, not Spock's) was "one to the tenth power"--which, scientific notation-wise, isn't really any better. But all in all, it seems to be a scripting error, not any actor delivery error.