There are four priority actions for policy rule. 'No change' is keep the priority setting of the frames.
'Set the packet's 802.1 priority' is replace the packet's 802.1 priority field with the value you set in the Priority field.
'Send the packet to priority queue' is put the packets in the designated queue.
'Replace the 802.1 priority field with the IP TOS value' to replace the packet's 802.1 priority field with the value you set in the TOS field.
'Replace the 802.1p priority by inner 802.1p priority' to replace 802.1p priority by inner 802.1p priority if there is an inner vlan tag.