If you confirm, then FlowJo will open a graph window for every sample in the current group which has an equivalent population to the one you are looking at. In addition, it will set the graph type and options so that the graph looks exactly the same as the current one.

If you wish to avoid this confirmation dialog window in the future, click on the "always use the same answer" box at the bottom left--FlowJo will remember your answer for the duration of this FlowJo session (regardless of the Workspace). The next time you run FlowJo, this dialog will return.