Available space

WD External Drives External Drives for Mac
2

Hello,

The only reason why one drive might display more available space that the other is due to the data that was transferred to it.

Can you check the amount of files that you have stored on both drive to see if there’s any difference?

Unless there’s an issue with the unit, you should be able to see a total of 1.8TB due to the conversion from Decimal to Binary on both drives.