What can you say about the actual maximum channel capacity?

The actual maximum channel capacity is defined by the Shannon-Hartley theorem, which states that it is determined by the bandwidth of the channel and the signal-to-noise ratio (SNR). In practice, achieving this maximum capacity is often limited by various factors such as interference, distortion, and practical constraints in encoding and modulation techniques. Therefore, while theoretical limits provide a foundation, the real-world performance often falls short of these ideal values due to these challenges.