I don't know if this was posted before. I did some searches and didn't find anything relevant. So, here's my problem.

I had a download of 1.89GB left over the night. In the morning I had to restart it because the network was disconnected and had to do some troubleshooting
After I restarted it I saw that it already downloaded 650MB and the download was going with 120-130K/s, although ktorrent reported me that the remaining time was 24 hours! Doing a little math you'll see that if the download was 100K/s constant the ETA would be about 4-5 hours.
Then, I saw something nice: in the status bar there was a message "Trasferred down: 120MB".

So what does "transferred down" mean and how is ETA calculated?

Yeah I see that too. Thought that it was just me but looks like other people are experiencing it as well

You can set an ETA calculation algorithm in options (I don't know since when it's available).