In plain words
Remove every adjunct by the words 'not this, not this'. What is left is the individual Self. Reflect on what the great sayings declare, its oneness with that supreme Self, primal and unsurpassed, and be clear about it.
Word for word
Removing all adjuncts through ‘not this, not this’, reflect and clearly understand the identity, declared by the great sayings, of the individual Self that remains and that unsurpassed primal supreme Self.