The Centurion said, "But just say the word, and my servant will be healed." He meant that if Jesus said the word or gave a command, it would trigger millions of mighty angels (under his control) to instantly act upon the word and fulfil it. These millions of angels are very powerful and are eagerly waiting for Jesus’s command to perform a miracle. Despite their great power, these angels cannot perform a miracle(on their own) without Jesus' command. These millions of angels are constantly looking at Jesus for his words and commands to do something. Jesus just say the word or command regarding my need, it can trigger millions of angels to perform the word or command instantly. For performing my miracle, millions of angels are not required; one angel is more than enough. The centurion recognised the enormous power and authority in the words of Jesus that it can trigger millions of angels to perform His word. Jesus just say the word and I will receive my miracle instantly.