Short Answer: No
Long Answer:
http://registrar.mcmaster.ca /getre...y.html#gloss_e
"Extra Courses are those courses designated at the time of registration as "Extra", which are not included as units toward completion of a student's program. The grades obtained in such courses will not be included in the computation of the Cumulative Average. However, they will be included in the computation of the Sessional Average and the Full-load Average."
Don't ever assume anything. This is how people get into trouble with the regulations already established by the University.