Numbers greater than nine don't usually require conversion from text, as at least by the English (US) speech recognition engine (non-speech platform; Not sure if that'd be different), they're written as numeric characters.
E.G. if you speak ascending numbers, they would be recognized as "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "10", "11", "12", ..., "100", ..., "1000", etc...