I think you need use the same scale for the legend. e.g. steps, and range as shown below across all your map sheets as well as the bar chart.
I attached the updated workbook for your reference.
Hope this helps
Hi ZZ, thanks a lot for your reply!
I didn't understand how you did it a first, but then I saw the opened dialog box in your screenshot that explained exactly how you did it!
Super and thanks again!
No worries, I am glad to help