Open a project, and then open the schematic that you wish to modify.

Click: File -> Run Script and select RunRenumberComponents

As shown below

The following window will then open:

“Component Name (No Number)” is the Designator which defaults to RL. If the component is not a relay then this will need to be modified such as R for resistor D for a diode etc. Enter an increment value and this will increment all devices with the same designator suffix that you have entered. The increment can also be a decrement by entering a minus value, e.g. -16, but care should be taken that the value does not take any designators to a negative value.