What had been odd about the prophecy made by sibyll trelawney?

What was odd was the fact that it could've referenced multiple people. It stated that a boy born near the end of July would defeat Voldemort but there were two boys born then, Harry and Neville Longbottom. Voldemort thought that it was Harry so he went to kill him and he ignored Neville. It remained unknown until the end as to whom the prophecy was talking about.