It looks like you took this screenshot from the Interactions Report.

@chriscas is right - "student interactions" register communication between you and the student, not students engagement in an assignment. Interactions are recorded when you contact the student via Conversations or when you leave a comment on an assignment.

It sounds like what you may be looking for is the Access Report. The course access report shows a summary of user participation in your course, but has to be enabled by your Canvas admins. This Canvas Guide has more information about Access Reports.