Devices shown in sidebar confuses me after migration

I sold my iMac and bought a 13" MBP Retina.

I used my external drive with a Time Machine backup on it, and migrated the data over to the 13" from that.

Screenshot attached shows in my sidebar: iMac, Macintosh HD and Remote Disc

In the Macintosh HD - specs are 281.65 TB available, which can't be correct, since the 13" has a 256 gb flashdrive

In the iMac - specs are showing a Remote Disc, along with a Macintosh HD with 249.77 GB, 281.65 TB free in the same spec under the icon

I'm so confused.

When I click the apple, about this mac, Storage, I see 174.27 GB free of 249.77 GB

In pink, it shows backups as 281.47 TB and also in pink it shows Photos 4.1 GB

Can anyone shed some light on this scenario?