If you want you can change Steam to show it's speed in megabits rather than megabytes. That way you can see exactly how it's doing without having to work it out yourself (roughly you times megabytes by 8 to get megabits - so 2MB is roughly 16mbit):
In the Steam client in the top right click Steam > Settings
In the pop up window click Downloads on the left
Tick the box that says "Display download rates in bits per second"