My internet speed variation

I am downloading 'Free Mega Game Pack for Linux' with 'Transmission Bittorrent client'. Suddenly I feel curious about my internet speed. So I look at 3 info source and found 3 type of result.

At first I look at 'Transmission'
It is telling that my My download speed is 16.3 KB/s

Then I look at my 'NetSpeed'. It showing that my internet speed is download:26.9 KiB/s

Now, I open the 'Device Details' on Net speed. It is said that my to download speed is 32.0 KiB/s.

I am confused about this speed variation. I don't know which is correct.