Hard sentences in "Introduction to Christianity"

I am reading Cardinal Ratzinger's "Introduction to Christianity", and I must say, the following sentences are impenetrable, at least for me. I have no idea what they mean:

To be sure, it is a characteristic of understanding that it continually goes beyond our mere ability to apprehend and attains the awareness of the fact that we are comprehended. But if understanding is the apprehension of the fact that we are comprehended, then that means that we cannot yet comprehend that fact once again [in a second moment of understanding]; it furnishes us with meaning precisely because it comprehends us.

Not grokking that. At all.

But the rest of the book is pretty good so far.