Only getting half of sync speed

Hi, I come back from work today and was told the internet had been playing up. Ran a few different speedtests which came back between 35-40meg but my sync speed is 80meg, the internet seems fine but the speed seems to be a literal half of what the sync speed is and I have the boost.

Currently synced at 79999 down and 19999 up

Could someone see if there is a reason for this, maybe a setting, an error on my account or something. Most files only download at 4-5mb/s when I used to get 8-10mb/s

Thanks 

Mike.