Memory cards just like harddriver dont come up as the dead on size you got, so a 128 Gb card will come up a something a little smaller.
With something really large you will see a bigger chunk lost, so that 4 Tb harddrive might come off as a 3.73 Tb drive
The 128 GB Toshiba sd card i currently have in my card reader come off as measly 115 Gb, and my 1000 Gb ( 1 TB ) external harddrive list as being 931 Gb