An objection asks: if Allah knows that a given person will not be punished, in what sense can there be a warning, and how can warning coexist with pardon? The reply distinguishes divine foreknowledge from the functions of warning, reward, and forgiveness.
For example, a general punitive rule can remain a real warning while a recognized exception allows pardon in a particular case. The exception does not render the warning meaningless.
This does not posit a change in divine knowledge, nor require every general threat to be an inevitable punishment of each individual.