It would have read:
1 year time credit towards pay; or
1 year time credit towards promotion; or
1 year time credit towards pay & promotion.
If you signed up with "1 year advanced towards pay" as semi-skilled - and "promotion" wasn't mentionned, then it is not applicable to the promotion.
As an aside, your "cadet time" would have been looked at (if) had you reported it when you applied. "Cadet Time" is not based upon "time" - it is based upon "the courses you actually did as a cadet". Some cadet courses are worth diddley squat. "Cadet Time" does NOT count towards service as "Cadets" are not members of the CF. If, however you did a specialty qual course while in cadets, it may - such as basic para.
As well, you can't just "apply" to have "anything" put towards getting your Corporals earlier ... accelerated promotions are not "applied for" in any way, shape or form by the member themselves; rather, the CoC must observe an outstanding ability by the Pte to perform at the next level and must then recommend that the Pte be accelerated.