Data Migration Issue from PC to Mac using external storage.

I'm using a Seagate Backup Plus 2TB to transfer data from my PC to my Macbook. I've successfully loaded (I think) the PC data onto the storage device, but when I connect it to the Mac and select External Storage, and the Windows 10.pvm filename on the storage device, I get the following error:

Required: 17179869184.0GB
Available: 326.3GB

I'm no expert, but it looks like it's taking the entire size of the external device, rather than the actual file size of the data for the transfer. If I refresh, there's no change. I've tried different folder names, and I am selecting the specific file (windows 10.pvm), to no avail.

I should mention that I initially tried to do the migration over the network, but it was going to take 36 hours, so I cancelled it and went for the external storage option.

Any thoughts? I'm happy to restart the whole migration, but Parallels is already installed, and I haven't been able to remove it from the Mac.

Rachel