Problems with Reader mode

Is there no ACK when using pulsar Reader mode? Because every time a Reader restarts, it reads the message that was read before. If there are multiple Reader instances, each Reader will read the same data, resulting in repeated reads, is this the design?

Start by reading the Reader mode behavior around acknowledgments, restarts, and multiple Reader instances. Compare the observed repeated reads with the documented design and determine whether the expected acknowledgment and restart semantics are defined; done means the behavior and any required change are clearly established.

Written by the indexing model from the issue text.