Ikhtiṣār can be judged against wording already mentioned, or against a conventional wording for the same message. These are different comparative baselines.
For example, ḥaḍara al-qāḍī al-yawm ('the judge arrived today') is longer than ḥaḍara al-qāḍī. Yet removing 'today' counts as sound concision only where timing is recoverable and not independently relevant. Simple deletion is not itself an accomplishment.