Please refresh how to use lower limit in QOS

My internet connection is a 7500kbps down sustained with a 512mb up sustained with a possibility of a 25000 momentary burst on initial connections.

I understand setting max limits on classes so they don't exceed a certain throughput.

Can someone tell me if I'm wrong when I say:

"To guarantee minimum throughput to certain classes, place those classes higher and set the minimum throughput for incoming to a level you require."

I know that this reasoning is flawed somehow.

I'm not quite sure...

Please refresh how to use lower limit in QOS