Maybe the config menu isn't reporting the right upload speed on ADSL.
I'm on an ADSL giving me a max upload of 13.5 kb. The config at 50% said 22 kb so I throttled it to 12 kb.
But then I figured out that none was uploading with a speed more than 1.5 kb. So I changed to 80% - the config menu reported more than double the speed I actually have, but real uploads are up to 10 kb and all is working fine.