Following the QoS guide on this site, I have set maximum Total Download Bandwidth to 24127Kbps that my DSL modem is reporting and enabled AAC. This way QoS works fine and seems to be following the rules correctly. However it looks like my internet is faster than that...if I set up max bandwidth to let's say 27Mbps it will peak at around 26500Kbps, but then QoS isn't as effective anymore but I can download at max speeds when there's full bandwidth available
I'm attaching screenshots from both router and modem's admin web GUI.

When total BW is set to 24Mbps:

When total BW is set to 27Mbps:

