Max Rate Up showing as slower than Data Rate Up

[#1]

My Data rate Up is shown as 16797bps but the Max rate up is shown as 15898bps on the log of my Asus DSL-AC68U.
Upload speed on OOKLA Speed test is shown as 16.08Mbps, Ping shown as 13ms
On the BTW Performance Test Upload is shown as 12.68Mbps, and latency shown as 27.5ms
There seem a lot of mixed messages here, a puzzle,  I'm wondering if it means anything significant?
Has anybody got any thoughts?

[#2]

Mine does the same, I an only guess the SNR drops after it's synced to so the max shows less than the actual sync.

[#3]

Thanks for that Mark_ , you could well be right, I'll ponder, and try to watch the SNR figs.