I have added this issue to the tracker:
Bug 2073 – When logging transfer statistics, recent transfer speed was logged instead of average speed of whole transfer

I guess in this case @becausewtf may be referring to the varied results between CPS and if you divide the bytes transferred by the elapse time.

2020-04-16 21:25:04.264 Copying finished: Transferred: 714,585,792, Elapsed: 0:00:58, CPS: 7,640,628/s

If we take 714,585,792 bytes transferred divide by 58 sec, we get 12,320,444 bytes/sec. However in CPS: it indicates 7,640,628/s. So is the CPS value recorded wrongly, or the elapse time is wrong giving rise to wrong calculated result?

Can you post a complete log?

I am confused by Elapsed vs CPS values in the four lines below.
Elapsed in line 1 is half of line 3. CPS in line 1 is less than line 3.

2020-04-16 21:25:04.264 Copying finished: Transferred: 714,585,792, Elapsed: 0:00:58, CPS: 7,640,628/s
2020-04-16 21:26:35.592 Copying finished: Transferred: 714,585,792, Elapsed: 0:01:21, CPS: 11,049,871/s
2020-04-16 21:28:56.358 Copying finished: Transferred: 714,585,792, Elapsed: 0:02:08, CPS: 8,373,450/s
2020-04-16 21:30:07.670 Copying finished: Transferred: 714,585,792, Elapsed: 0:01:04, CPS: 10,860,950/s