Dell M6220 User Configuration Manual page 1170

CoS queue 4, with a 50% minimum bandwidth guarantee. Lossless traffic
classes generally use the default WRR scheduling mode as opposed to strict
priority, to avoid starving other traffic. For example, the following commands
assign user priority 4 to CoS queue 4 and reserve 50% of the scheduler
bandwidth to CoS queue 4.
classofservice dot1p-mapping 4 4
cos-queue min-bandwidth 0 0 0 0 50 0 0
1170
Configuring Class-of-Service