score:5
I'm pretty shocked to hear that a US consular officer did not understand the VWP 90-day rule and misrepresented it to you, but that appears to be what has happened.
First, the important bits:
If you have exited the US before the 90 days are up, you are not overstaying in the US. You're in some other country. This applies whether you're in Canada or Cameroon, Mexico or Malta. Doesn't matter for the purpose of leaving the US, so long as you leave.
The so-called 90 day clock is a tool that helps to discourage visa runs. That is, someone tries to spend a large amount of time in the US, leaves for a short period and then returns. If they are within the original 90 day period, they will only be readmitted until the end of that period. If they are outside that period, they could theoretically be admitted for another 90 days, but it's very likely they will instead be detained and questioned very closely about their travel plans.
Someone who has spent three weeks in the US followed by four months outside the US has absolutely nothing to worry about with regard to this rule, even if that time was spent in Canada, Mexico, etc.