Nothing. The Court of Appeal says what the sentence in the case should have been, and that's that.
What sometimes happens is that the Court of Appeal decides that a given type of crime is not being sentenced severely enough. When that happens , the very next case they get with what appeared to be a harsh sentence in the court below is used by the Court of Appeal as an opportunity to lay down the law and to make speeches telling judges to be harsher in future. And of course, they uphold the sentence (always assuming it's not so wildly out as to exceed even their wishes).
This might just be such a case.Or such a case may have happened between this one and the appeareance in the Court of Appeal . Even so, and that said, 5 years,first offence, even on a plea of guilty, to possessing crack with intent seems right.