Since it has been added to fonts in the 90’s, the Euro symbol only certain value is its Unicode point of 20AC. The site you refer to describes the ASCII position chosen at the time by Microsoft for Windows. At the same time, Apple had chosen the ASCII position 219 (which was previously “currency” ¤ that Microsoft places at 164). In early 90s fonts, then, there is no Euro symbol and you will probably get a rectangle. In modern fonts, thanks to the magic of Unicode, you will get the Euro symbol no matter if it is at position 128 or 219.
Actually, the value of 226 maybe right as well, but you do not have to worry about it. Let the system deal with Unicode points transparently.
Encoding is like health : as long as it is good, nobody thinks about it. Only when health fails, or when an app starts displaying weirdos like black lozenges with a question mark over them, you think about aspirin and encoding 