How to correctly interpret output from the sync command?

I am currently using the rclone sync command to go from Dropbox to Google Drive. I have been getting information like the following:

2018/11/12 03:38:21 INFO  : 
Transferred:   	    2.455G / 2.851 GBytes, 86%, 25.391 kBytes/s, ETA 4h32m26s
Errors:                 1 (retrying may help)
Checks:             55125 / 55125, 100%
Transferred:        23170 / 33182, 70%
Elapsed time:  28h10m0.4s

I am wondering what Checks and Transferred means. Why would one be at 100% and the other at 70?

Checks are seeing what is already on the other side and comparing it to what is local.

Transfers are when it has to move a file over so they can be different.