FortiGate session table, a flag "none"

[ramunas]

Hello, this link explains most of state= flags, such as "local", "redir", "dirty", etc., https://kb.fortinet.com/kb/viewContent.do?externalId=FD30042

but it doesn't explain a flag "none". Does anyone know what it means? Example diagnose sys session list session info: proto=6 proto_state=01 duration=4599 expire=2753 timeout=3600 flag- s=00000000 sockflag=00000000 sockport=0 av_idx=0 use=3 origin-shaper= reply-shaper= per_ip_shaper= ha_id=0 policy_dir=0 tunnel=/ vlan_cos=0/255 state=log may_dirty npu none log-start statistic(bytes/packets/allow_err): org=1549/20/1 reply=1090/15/1 tuples=2 speed(Bps/kbps): 0/0 orgin->sink: org pre->post, reply pre->post dev=15->17/17->15 gwy=172.20.121.2/5.5.5.33 hook=post dir=org act=snat 5.5.5.33:60656->91.190.218.66:12350 (172.20.121.135:60656) hook=pre dir=reply act=dnat 91.190.218.66:12350->172.20.121.135:60656 (5.5.5.33:60656) pos/(before,after) 0/(0,0), 0/(0,0) src_mac=98:90:96:af:89:b9 misc=0 policy_id=1 auth_info=0 chk_client_info=0 vd=0 serial=00058b9c tos=ff/ff app_list=0 app=0 url_cat=0 dd_type=0 dd_mode=0 npu_state=0x000c00 Thanks