mb and Mbits is the same thing... what it translates to is a guess because its the server at the other end i.e, Steam, Gog etc which gives you your data and the speed of that flow could be anything from zero up
assuming servers don't crash like they have every other release then a stedy flow of 15mb will be much faster then 1-25 mb jumping all over the place, thats 150,000 mb so 10, 000 sec or 3 hours
but in the real world if you get half that speed i.e, 6 hours without a crash then you would be lucky
