Verse 6

6.  This is the Lord of All the Omniscient; the Inner director the Source of All.  This place is the beginning and end of all beings.

"This is the Lord of All the Omniscient"

This is the "state" of Self that transcends the other three states.
This  "Self",  beyond experienced states is as described,   "the Lord of All the Omniscient"  which means this  "Self"  is the knowledge that supports the apparent duality of forms of manifest Creation.
This is the state of the  "Self"  before manifestation of the Universe and after the return of the universe to unmanifest Knowledge.
This is the  "Self",  as the Non-Dual Absolute.

"the Inner director the Source of All".

The apparent individual within the duality and Maya of creation is nonetheless  "directed"  by Absolute Knowledge as all that exists is.  This  "Inner director"  of the being has been called the  "self"  hence the name  "(Absolute)  Self",  the One  "Self"  of the duality  "self"  within creation as we have described previously.

"This place is the beginning and end of all beings".

If this place is  "the beginning and end of all beings"  then it is confirmation that we have arrived back to unity with the Absolute in the  "fourth quarter".
It is from the Non-Dual Absolute that all that materially exists is made manifest,  and it is to this Unity that all forms return on the cessation of desire.

This same unity of  "Absolute Self"  Consciousness is also approached by the meditating Sage through stillness and the intuition of Buddhi and intellect.  This access or closeness is known through  "self"  or the inner director.  Through this intuitive closeness or perhaps openness,  Divine Truth becomes known.
We are told by the subtle intellect,  the Rishi and these words of the scriptures of this access to divine truth,  but any actual  "process",  as it were,  is not witnessed or does not come into the awareness of any of the states of consciousness.

 

The meaning is,

Which quarter is the One quarter that knows all other quarters or states, but at the same time is unknown by those three states?
Which quarter is the One quarter that provides continuity or unity to the other three?
Which One quarter is it that through the very fact of its existence allows the other three quarters to "imagine" themselves as being a complete entity?
Which one quarter is it that allows the other states to rise and fall, come into apparent being and apparently to fall out of being?
Which one "Quarter" is Eternal.
What is it that Alone Truly Exists?
           This is to be realised.