This paper studies the effect of bundling groups of contiguous carbon and tungsten ionization stages on the calculated impurity screening. EDGE2D/EIRENE was used to calculate the charge state distribution in the SOL and the edge of the plasma core, which resulted from the puffing of either atomic carbon or tungsten at the JET outer mid-plane. The input parameters were constant for a number of code calculations where the only parameter changed was the number and/or charge states bundled in either carbon or tungsten. In this manner, the effect of bundling on the carbon or tungsten screening or fuelling efficiency was determined. For carbon and tungsten there was only a weak dependence upon the actual bundling scheme used.