Is there a chance you reset your iPhone once you got it? That could be why your counter is off. But either way, the data counters on any phone is never the best and what is listed on Koodo's site will always be taken as correct.
I have the same question as Christopher. After reading your reply, I'm wondering why Koodo's tracking is taken to be correct v.s. your phone recording the data as you're using it? If it's a discrepency of 10 MB, that's not too big of a deal. However, this month I reset my iPhons SE's cellular usage stats at the same time as my new billing cycle. My phone recorded 3.6 GB of use and Koodo recorded 5 GB. That's a significant difference, and enough to question if their current method of tracking our data usage is correct.