There are many disciples under Sakyamuni Buddha's seat to testify for Arhat grosvenor. Usually in Buddhist scriptures, it is often said that' 1,250 great monks are known by the great arhat'. People often say that the eighteen arhats are actually sixteen arhats, and the other two were added later. Before the Buddha died, he instructed sixteen disciples to live in the world for the benefit of all beings. They are: Venerable Dubin Barololo/Arhat Kanakavatsa/Kanoga Luo Li Lazy Venerable/Venerable Suvinda/Venerable Nogiro/Venerable badra/Venerable Caledonian/Venerable Lavalodoro/Venerable Boga/Venerable Semitoga/.
Another correction is that Tathagata and Buddha are honorifics for Buddha. Just like professors and teachers, we can say that a professor or a teacher is someone. If we say that the teacher is a professor, we don't know who we are talking about. Folks often say that Tathagata is a misnomer, but it should actually be called Sakyamuni Buddha or Sakyamuni Tathagata.