DU SUNGS

This is the last part of the second line, du sungs. du is a particle, a sub-ordination particle, it has wide use, but think of it as organizing something on the right side to the left side. In this case it's a verb that is organizing something on the left side.

The verb is gsungs, and is there a verb you see a lot in texts, this is it. gsungs means taught, or said. It's used a lot in commentaries to end a quotation of a teacher, and the quotation ends with gsungs. Note again how the verb is usually at the end of the sentence.

So, roughly the second line is: The Able one taught for the purpose of Discriminating Awareness.