Error when input new parameter in Fluent
 

It is quite strange for me when I try to use 'input new parameter' in fluent.
For example, when setting up the boundary condition, select inlet and click edit. Choose velocity as magnitude and direction. Then click the drop list on the right of velocity magnitude and choose input new parameter. A new window comes out and input any value such as 10 in the current value, then click OK. However, no new parameter of velocity has been added!
'Interesting' thing is, when I click cancel rather than OK, a new parameter with value of 0 will be added!

To set a new input parameter is a simple task but I don't know why it happens so difficult to me....