250kBs that's 2000 of the 100000 bits per second I was sold (10 megabit connection)
Nitpick: that's 2000000 (2mbit) of 10000000 (10mbit)
Download rates actually typically decrease when your upload rate increases even though the connection is bidirectional and should have no issues doing both at once.
This is because when you download, your computer send packets back to the source to say "Yes, I got this". So, if you use the upstream for uploading a file, the download can't get its packets out fast enough to keep up with the downstream.