The court keeps track of all sorts of statistics including average time a case remains open, whether the case is compliant with the time standards, whether a case is open or closed, etc.
When a case is closed, you may have the right to reopen it, however, it may be closed under the criteria the court uses for its statistics.
Your case is closed according to the court, but they don't want to mislead you by saying it is closed, if you have some residual rights, therefore it says "closed statistically."
This term is usually employed to close out probation cases when someone has been placed on probation, not when the court examines its statistics in a regular criminal case. Criminal cases are not generally closed "statistically" because they must be resolved through a trial, dismissal or plea. When a probation case is closed statistically it generally means that while the matter may have been subject to a violation, the probation agency is making an administrative decision to close it on its books, with Court approval.