From what Robbie and Alexandra have told me,
从Robbie和Alexandra告诉我的情况, 看来
is as the proportion of the total vocabulary of his mother tongue against those words of his own baby talk that are taken up into the vernacular of his family.
就好像他本国语言的总词汇量和自己咿呀学语时他家庭所接纳的他的词汇量之比。