This has been an issue for a very long time. If I try to throttle my download speed in the blizzard app, it has some weird multiplier on it. So if I want 10 MB/s I have to set it really to about 12-13 MB/s (10MB/s throttle is only around 8 MB/s). If I want 40 MB/s I have to set it around 70 MB/s.