It is that when on a successful prosecution appeal against sentence the appellate court imposes a more lenient sentence than it considers the sentencing court could have properly imposed, it is reflecting a sentiment behind the principle against double jeopardy.
"13 It has been explained that what is referred to as the rule against double jeopardy is a manifestation of the principles expressed in the maxim nemo debet bis vexari pro una et eadem causa (a person shall not be twice vexed for one and the same cause), which is the foundation of the pleas of autrefois acquit and autrefois convict ... . The underlying idea is that the State should not be allowed to make repeated attempts to convict an individual thereby subjecting him to embarrassment, expense and ordeal and compelling him to live in a continuing state of anxiety and insecurity as well as enhancing the possibility that even though innocent he may be found guilty. The rule is properly understood as a value which underpins the criminal law." [case citations and internal quote marks omitted]
There is an interesting difference between the Criminal Procedure Act 2000 (Vic), ss 289(2), 290(3), and the Criminal Procedure Act 2011 (NZ), ss 251, 257. The former specifically directs the appellate court not to take into account any element of double jeopardy involved in the appellant being sentenced again, whereas the latter makes no mention of this.
I suppose that in assessing the results of the unspoken competition between law reform bodies to come up with the perfect criminal procedure laws, Victoria should be penalised on this point. At least that is so unless you think that, willy nilly, the offender should get the sentence he deserves, later if not sooner.