The residual risk (RR) is the score once the control measures have been implemented for the specific hazard.
On the standard HANDS HQ matrix the severity of harm will still be the same but the likelihood of harm should reduce.
E.g. If the harm is a broken bone and very likely it will score 20.
If the control measures are sufficient the harm will still be a broken bone but it will now be very unlikely it will occur so the RR is now 4.