What prophecy of Calpurnia's do Brutus' ans Messela's letter confirm?

Calpurnia's prophecy, conveyed in her dream, warned Caesar of danger, specifically that he would be harmed on the Ides of March. The letter from Brutus and Messala confirms her fears by highlighting the conspirators' intent to assassinate Caesar. This aligns with the ominous signs she interpreted, ultimately illustrating the tragic fate that befalls Caesar despite the warnings.