Copied SD Card to Larger SD Card but size doesn't match?

[airtas]

I took my 64 gig SD card, moved it to Desktop and then moved those files to a 128 micro SD.

The old card was 56 gigs used and the new was 55.

All my important stuff is there but wondering why the 1 gb difference?

 

[SpookDroid]

Probably hidden/system files that aren't directly copied over.