I strongly doubt that you will be refused for this honest mistake. I’ve seen many cases in which applicants made a honest mistake in their application form, and they’re already a canadian citizen. Worst case scenario, they will ask you about this honest mistake in the interview, and you will explain the situation truthfully. In addition, even if you declared a simple wrong number in your presence application form, it doesn’t mean that they automatically refuse your application, considering the fact that your presence days will remain the same even with this honest simple mistake.
They already have all your entry dates to Canada. Don’t worry. Just send a webform and explain your honest mistake clearly. I’m pretty sure you will be fine. Just send the webform and explain it.
Good luck my friend and don’t forget that webform.