Once you have completed the output specifications for you MIKE 21 ST run, an estimate of the disk space (in Mb) required to save your output files will be shown in the Size of Output entry of the Output Size section. The disk space required depends on the extension of the sub-area used in the simulation of the transport rates, whether you chose to save results for transport time series or not and, if you did, the extension and time step of your simulation period.