Assuming it comes back through the portal, and it took 4 seconds with no portal.

Your stopwatch will measure 4 seconds when the portal is there.

A stopwatch in the ball will measure 4 seconds when the portal is there.

If you want to take stepwise measurements based on your clock, the ball will be at time 1 sec before going through the portal, time negative 1,767,225,598 when it hits the wall, 3 sec after it exits the portal second time, 4 sec when it reaches you.