This setting will be used when new Policy Rules are created. It defines how large the data volume for a transfer may be.
Please note that this is not the setting which will be used when a transfer is being performed. It is just a preset for new Policy Rules.
For a Cryptshare Transfer the maximum size for a single transfer can be defined. It is determined by the sum of the sizes of all files attached to one transfer. So if you set the limit to 2.000 MB, you could for example upload one file with 2.000MB or up to 10 files with 200 MB at a time.