What could be the issue here? How can I reflect the displayed digital places from the desktop to the server?
When you change the number of decimal places in ArcMap you are changing the display of the number not actually truncating it. So if the original number had 8 decimal places it still has 8 decimal places even if you chose to display it as 3.
I would say this display is a property of a Layer object and not a Feature Class, so if you are displaying data direct from a Feature Class in ArcServer then it is not surprising that you are seeing the full number of decimal places. You need to be viewing a Layer object from ArcServer if you want to impose a restriction on the number of decimal places. I don't use ArcServer so I leave that to someone else to answer.