I am a male 46 , my theorical max hr is 176, but running last mile my hr is 189 in according to my garmin hr monitor, then my real max hr is?

MPHR: Maximum HR is just a number we throw out based on a formula. The max HR you measure is yours. Some people can do more than their "predicted" and other can do less. Sometimes monitors can be deceived so best to check a pulse directly at your wrist or carotid artery in neck.

Remember : The typical formula of HRmax = 220- age isn't perfect and in fact an oversimplification. It's a good jumping off point but depending on the study you look up, you could find many different formulas - most more complicated than above. In the end, your exact maximal heart can only be determined through exercise. But realize with elevated heart rates your monitor may be less accurate.