There are four DiffServ actions for policy rule.
'No change' is keeping the TOS and/or DSCP fields in the packets.
'Set the packet's TOS field' is set the TOS field with the value you configure in the TOS field.
'Replace the IP TOS with the 802.1 priority value' is replace the TOS field with the value you configure in the Priority field.
'Set the Diffserv Codepoint field in the frame' to set the DSCP field with the value you configure in the DSCP field.