exactly. see extract from web that explains better than i could.....
In most countries, including all of those of Australia and Europe the "headline" octane rating shown on the pump is the RON, but in Canada, the United States and some other countries, like Brazil[4], the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI, and often written on pumps as (R+M)/2). It may also sometimes be called the Road Octane Number (RdON)
the whole articale is here...
Octane rating - Wikipedia, the free encyclopedia
and goes on to show all the fuels commonly available and how they are marked differently in different places.
Getting back tot he original question, someone must be able to advise what the consequences are of putting fuel in that has too high an octane reading? 98 RON fuel over there looks like it would be labeled as premium 93 octane here in north america.