It means that action on the offense has been postponed until later. There could be several reasons for this, but the two most common are:
1) The person reviewing the offense doesn't know what to do or decided that a second opinion is needed, and it will have to wait until somebody else looks at it later.
2) Jagex may be making changes to the rule that covers the infraction, and the decision will be made when the rule is changed.
Don't be surprised if the infraction is decided later, either by blackmark/ban or by removing it.