Approximations for the mean performance indices for the M/G/c queue rely on the approximate computation of the probability that an arriving request has to wait for service and of the minimum of residual service times if all servers are found busy. Using numerical examples, we investigate properties of these two quantities. In particular, we show that the minimum of residual service times depends on higher order properties, beyond the first two moments, of the service time distribution. Improved knowledge of the properties of the two quantities studied in this paper provides insight into avenues for improving the accuracy of approximations for the M/G/c queue.