2015英语二，翻译Most of the first-generation students

2015英语二，翻译Most of the first-generation students
Most of the first-generation students (59.1 percent) were recipients of
Pell Grants, a federal grant for undergraduates with financial need, while this was true only for 8.6 percent of the
students with at least one parent with a four-year degree.
能不能翻译一下？
尤其是was true only for 这里什么意思?