Or twice, in exceptional circumstances.
Guys don’t ask for directions. And they don’t like getting advice, even if they’ve asked directly for it. He did hear you the first time. Even if he turns away, looks blank, starts doing something else, and doesn’t respond, he heard you.
If you repeat what you said a couple more times, just in case you think he didn’t hear, there’s a chance he’ll do the opposite of what you want, just to annoy you.