The purpose of this initiation is to attune students to the energies in such a way as to enable them to teach Reiki to others.
The traditional Usui method uses the three symbols learned in Reiki 2nd Degree plus the Usui Dai Ko Myo.
The Tibetan Master attunement uses those four symbols plus the Tibetan Dai Ko Mio & the Tibetan Fire Serpent.
Many students feel that the addition of the Tibetan symbols creates immense extra power.
Test the symbols for yourself & use whichever feels right for you at any given time. Use the Usui symbols only & then the Tibetan symbols only so you can feel the difference in the energies.