The ionic conductance of a solid-state nanopore plays an important role in analyzing biomolecules transported through the pore. The phenomenological pore-conductance is assumed to be a sum of three contributions: bulk, surface (for a charged nanopore) and access ones. Despite being commonly used, phenomenological results were not rigorously derived in theory and their accuracies have not been tested yet. By carrying out numerical modeling on the nanopore conductance, I show that both the ion concentration and the surface charge can affect the accuracy. For a charged solid-state nanopore solvated in an intermediate-ion-concentration electrolyte (e.g. 50 mM), the phenomenological result can be substantially larger than the numerically calculated one. The criteria for properly applying phenomenological results are provided.