Understanding how the composition of cellular automata rules can perform predefined computations can contribute to the general notion of emerging computing by means of locally processing components. In this context, a solution has been recently proposed to the Modulo-n Problem, which is the determination of whether the number of 1-bits in a binary string is perfectly divisible by the positive integer n. Here, we show how to optimise that solution in terms of a reduction of the number of rules required, by means of a merging operation involving of the rules´ active state transitions. The potential for a more general usage of the merging operation is also addressed.