What is the default action for the SYN Flood option within the DoS Protection profile?

Random Early Drop —The firewall uses an algorithm to progressively start dropping that type of packet. If the attack continues, the higher the incoming cps rate (above the Activate Rate) gets, the more packets the firewall drops. .. (https://docs.paloaltonetworks.com/pan-os/9-1/pan-os-admin/zone-protection-and-dos-protection/dos-protection-against-flooding-of-new-sessions/configure-dos-protection-against-flooding-of-new-sessions)