Some statements require an unexpressed element for the intended proposition to be legally or semantically sound. This is iqtida al-nass. The interpreter is not free to invent missing words; the supplementation must be necessary for the statement's validity or coherent truth.
Ask whether the intended statement remains sound without the implied element. If it does, adding a preferred new qualification is not a justified use of iqtida. Necessity distinguishes this mode of indication from arbitrary insertion.