The old form is very explicit regarding work and address history and I doubt that this will change on the new form:
If you miss any period of time during the relevant period, your application will be returned to you.
What I would do in your position is to list those three days as in transit. So simply put the exact dates of being in transit and if you want to be extra double sure write "see attached explanation". Then attach a document saying "Explanation regarding Question X" and explain that it took you three days to get to Canada, where you transited, what you did for the three days (I would assume you had some overnight hotel stays).
That is my recommendation.
The most important one is: Any gap will lead to refusal of your application. It says so in the form!