Avg rate exceeds Max Limit

I noticed often internet starts lag badly, even netwatch script i made to ping google servers and play a tone on net down activates as net was down just because of this.

Upload is getting choked on DSL modem but i set rate below our maximum DSL upload speed (around 10% less)

But see screenshot/s, upload goes to 6.9 Mbps, while i set max limit of 5900k and burst limit to 6M, why this happens?