法華玄義釋籤 1.39

1.39

「作如是說」者，總舉所說。「我少」等者，別示說相。十九喻城，三十成道，不說爾前，故云「我少」。

"Speaking such words" generally raises what was spoken. "I, when young..." and so forth separately show the aspects spoken: leaving the city at nineteen and attaining the Way at thirty, not speaking of what came before, hence it says "I, when young".