Assigning Tasks to Employee in WCB, but still task available to other users.

We have created 5 tasks and all 5 tasks appearing in WCB in pending staus. Warehouse manager manually assigned 3 tasks to X and 2 tasks to Y and no priority is assigned to any task.

All the tasks belongs to Same "user task type" and both X, Y are in same in same resource group which is assigned to the "user task type".

So now when X logged in he should see only the 3 tasks assigned to him, and when Y logged in he must see only the 2 tasks assigned to him, but this is not happening, Both of them can see each others tasks, Any one can guide how to restrict that, X should see only his tasks not of Y's ?