Unless it has changed in the last year it is as stated grades 10 - 12. Sons both currently at RMC (in first and fourth year) were both told this and what the average was that was going forward. You should ask the recruiting centre or registrar at RMC if unsure or want to know when it is applicable. (Assume that as both sons were told that they will tell you, but that may not be the case) They are looking for consistent strong performance not someone who can turn it on only when they feel required.
They were also asked for their first term grade 12 report card, which unless you are in a non-semestered school for all courses will have some final grade 12 marks... and were told that they look at the others as well as half way through the year although do not go into the average.
Not sure how it is done if you have extra courses... if they use those required for your selected degree and the best number to a total of ?? Or if all used for every year. If you have any question with this I recommend that you contact the registrar at RMC and ask.
It is RMC that decides so they would be the best place to seek a definite answer if you need one.