I wasn't exactly saying that you only needed to send and highlight a few dates. If CIC requested your entries for (say) January 2011 until January 2015, you would send all the pages that show entries between those dates. If that's 147 pages, then you would send all 147 ages. The RQ will indicate what period they are interested in, so you just have to follow what is written there. It's not like you can hide your many crossings, because they will also show on the Canadian report as entries into Canada, and CIC has access to that information. However, yes, a cover letter explaining your crossings is a good idea.