Hi @ElZakariyae, welcome to the forum!
According to your screenshot, your WARN/CRIT threshold for “Time since last sync” is two (2) hours, resp. (4) hours. The check result reports, that your last sync was eight (8) days and eight (8) hours ago. The CRIT condition is fulfilled, so you get an alert.
If you want to change this behaviour, you need to modify the corresponding rule. In my Checkmk 2.0.0p21 instance, the rule is called “State of NTP time synchronization”.
HTH,
Thomas