副词修饰介词短语

Translating consists in reproducing the closest natural equivalent of the source-language message,  first in terms of meaning, second in terms of style.

这里的first和second是副词修饰介词吗？还是省略了成分。

Translating consists in reproducing the closest natural equivalent of the source-language message,  first in terms of meaning, second in terms of style.

没省略成分。这是顺序副词修饰介词短语。