Maximum Data Rate

[#1]

Was just wondering what the difference is between these 2 values? As far as I know the 1st value is my Synch Speed which after overheads gives me approx. 18/73 throughput but not sure what the second values correlate to.
6. Data rate: 19999 / 79906
7. Maximum data rate: 28955 / 90455

[#2]

it is what your router thinks you could get if there were no external restrictions