# Naive Bayes classifier & the probability distribution

I have posted this question to the programming stackoverflow as it is something I have came upon as a programmer but it's more a math problem.

I'm using PHP module called TNT Search for text classification and the documentation states it uses the Naive Bayes classifier. I can't find the probability distribution function for its outputs though. I would have guessed that it's some kind of Gaussian distributions but the values I get from the program are in the range of negative floats ranging from about -20 to -10 - the less the more is the program sure with its result.

How can I find a correlation with percentual probability from the data I get? In another words I want to find a value that would correspond for example to 33% credibility.