the ZF 5HP19 is a 5 speed gbox with TC lockups in the 3rd, 4th and 5th gears. so in effect it could virtually do 8 different ratios. the TC lockup is set between 2500 till 3000 rpm and the lock up is initiated depending on all other inputs ie driver driving style, throttle position, vehicle inclination angle, road speed, rpm etc.
so at the 5th gear you could have 2 different road speeds at 3000 rpm depending on TC lockup. generally when the TC locks up the RPM will have a drop of 500.
apart from the TC functionality, when full lockup is done, some may still slip due to the worn friction lining on the TC housing. this will again effect the speed.