This is used for restart files. If you have a previous file you wish to restart the current run from, put the PREVIOUS run name (minus the _g01.cdf)
For example, if you ran a model from 0s - 7200 s, and you now want to run from 7200 s - 10,800 s, you would use the 0-7200 run name.
If you are not using a restart file, the restart name should be set to “nada”