The compound in question, and the name generated by ChemSketch:
Now, I am confused at the first point: when we have to select the parent carbon chain. For this compound, I would have selected "benzylamine" as the parent chain, as it obviously has more number of carbon atoms and more unsaturation than both methyl and propyl. Thus, my preferred IUPAC name would have been "N-methyl-N-propylbenzylamine".
But, for some reason "propane" is the main carbon chain here instead. So, what is the logical reasoning for the naming these tertiary amines?