This panel is just for RED interface and it is used to specify the maximum amount of bandwidth available in both outgoing and incoming directions.
VLAN isn’t still supported on Traffic shaping, you need to define a CIDR object with the VLAN network and make small trick by shell, this command will create a new rule:
db tc set "cidr;your_new_cdr_name" ip Description "Low priority" Priority 3
signal-event firewall-adjust