We have noticed that, when a timed assessment is sent because its time has expired, the related event is "sam.assessment.timer_submit" instead of "sam.assessment.submit", which is sent when users sends their assessments themselves.
Looking in Site Stats, the number of sent assessments is counting only the ones that users have sent, not the automatically sent ones.
Steps to reproduce this:
1) Create a timed assessment (i.e: 1 minute) and publish it
2) Complete and send the assessment with one user before time expires.
3) Complete the assessment with another user but let time expires instead of sending it.
4) In Site Stats, only one sent assessment is shown.