Multiply-Accumulate Operation (MAC)- Computations in NN network involve a multiplication and then an addition and are thus referred to as Multiply-Accumulate Operations (MACs). These (32/63/128/256) configuration of U55 means that (32/63/128/256) number of 8x8 MACs/cc supported in respective version of the config of U55.Note the higher the MAC config, more will be number of DPUs(dot product unit), adders, area size, power etc.