I'm not sure accurate their system is anyway. When I did my application for Nexus I listed all the countries I had been to. Only to be questioned about other countries during my conversation with CBP. The thing was, all the countries listed were ones that my partner had visited and listed in her application.

After a confused back and forth he wrote it off as an IT effup (which he admitted happens with significant frequency) and altered the info and we moved on to other questions.

So I don't think you have anything to worry about, offer to correct it during your interview and that should be it.