SAML clock skew issue

Hi I'm trying to implement SSO with the IDP Authentik in a local environment. But the log said that I have this clock issue:

__samld_sp_login_resp [847]: Clock skew tolerance: 0  __samld_sp_login_resp [852]: Clock skew issue. samld_send_common_reply [91]: Code: 5, id: 1, pid: 3728, len: 53, data_len 37 samld_send_common_reply [99]:     Attr: 22, 12, f samld_send_common_reply [99]:     Attr: 23, 25, Undefined error. samld_send_common_reply [119]: Sent resp: 53, pid=3728, job_id=1.

And the datetime is just the almost the same from both sides:

$ date Tue Aug 27 01:04:39 AM +07 2024

FGVMEVL-CYXEDR9C # get system status System time: Tue Aug 27 01:03:49 2024

and I don't use NTP server on Fortigate side:

FGVMEVL-CYXEDR9C # get system ntp ntpsync             : disable type                : custom syncinterval        : 60 ntpserver: source-ip           : 0.0.0.0 source-ip6          : :: server-mode         : enable authentication      : disable interface           : "fortilink"

 Can anyone explain and help me to fix this issue? Thank you.