Can you explain why in the AMS terminal list page ,the Reg. user Column is showing 1000/3000,but the actual registered user in the DB is 1553/3000?

For your information, the Reg. user column info.under AMS terminal list page will only be updated when there was a data changed at the registered device e.g.update user name or add new users etc.

    So you can Login to the register device's [View User List] to click any User ID,and then add one more space at its other name so that the data changed will be made and updated to AMS database accordingly