Hi Chelsea - apologies for the wait; I can be a bit slow to respond to questions.
I'll need your source's ID-number or name to be sure of this situation, but one thing that can commonly confuse folks is the difference between "Last classifier saved" and "Last classifier trained". CoralNet should be consistent about training a new classifier when your confirmed-image count has gone up enough, but that newly-trained classifier may not get saved if the evaluated accuracy hasn't improved enough since the previous classifier.
You can get more info on recent classifier trainings by clicking the "Jobs" tab at the top of your source, and applying the filter "Type" = "Train classifier".