The jurisdictional limits do not create a ceiling from which the appropriate sentence should be calculated. If it did, taking a purely mathematical approach, where the jurisdictional penalty limit is two years, and the offence is one of a ‘medium’ level of seriousness, then (absent all of the other sentencing considerations) the appropriate sentence would be one year of imprisonment. This is not how the sentencing process works.
It’s the upper limit for the specific offence that provides a guide to sentencing, and is only one of a number of statutory and common law considerations factored into the instinctive synthesis: s 5(2)(a) Sentencing Act 1991. If the matter is potentially too serious to be dealt with in the Magistrates’ Court, the Court may refuse application for a summary hearing: s 30 Criminal Procedure Act 2009.
While this may sound obvious, the jurisdictional issue came up again recently in Dankovic v The Queen  VSCA 255. The (unrepresented, it would seem) accused mounted the argument in her written submissions to the court that, because her deception offences could have been dealt with summarily, the County Court judge who sentenced her should have considered himself constrained by the Magistrates’ Court’s limits.
Nettle JA [at 18, Maxwell P and Ferguson AJA concurring]:
That argument is also untenable. No doubt, the charges could have been prosecuted in the Magistrates’ Court, as the judge observed. If they had been so prosecuted, however, the maximum penalty for each offence would still have been as it was in the County Court. Section 28 of the Criminal Procedure Act 2009 (previously s 53 of the Magistrates’ Court Act 1989) enables indictable offences to be tried in the Magistrates’ Court in certain circumstances. If they are so tried, s 113 of the Sentencing Act 1991 provides that the Magistrate cannot impose a greater sentence on any one charge of more than two years’ imprisonment; and s 113B provides that the total effective sentence may not exceed five years’ imprisonment. But that does not mean that the maximum penalty for any offence so tried is reduced to two years’ imprisonment. As Brooking J explained in Hansford v His Honour Judge Neesham & Ors:The same point was made by Nettle JA [at 20] in regard to s 113A in R v Duncan  VSCA 137.
Where a court tries an indictable offence summarily under s 53(1) of the Magistrates' Court Act and convicts the defendant, by s 113 of the Sentencing Act, the maximum term of imprisonment to which the court may sentence the offender for that offence is two years. But this does not mean that two years is ‘the maximum penalty prescribed for the offence’, to which the court must have regard by force of s 5(2)(a). That phrase is confined to the maximum penalty selected by the legislature as that which should be prescribed for a particular crime. Section 5(2)(a) is in no way concerned with the limitation imposed by s 113 upon the jurisdiction or powers of a sentencing magistrate, whereby, whatever the nature of the offence, and whatever the maximum penalty prescribed for it, the magistrate may not impose a term of imprisonment greater than two years for the offence. Section 113 operates indifferently upon all sentences to be imposed for an indictable offence tried summarily under s 53(1). It does not prescribe a maximum penalty for the offence in the sense in which those words are used in s 5(2)(a), the specification of a maximum penalty by the legislature for a particular crime. It leaves the statutory maximum penalty untouched, but imposes upon a particular sentencing court a jurisdictional limit. It imposes its own maximum, not by reference to the nature of the offence and its gravity in relation to other offences, but by reference to the status of the sentencing court ....
The judge who sentenced Dankovic stated in his reasons that he did not exceed two years imprisonment for any single charge (there was some cumulation between charges) in recognition of the fact that the matter could have been dealt with in the Magistrates’ Court. But his Honour wasn’t obliged to do that, and certainly didn't have to treat two years imprisonment as the maximum penalty reserved for the most serious of cases.