The DHCP Fixed Leases table
only shows entries that you enter into the MAC Address and IP Address boxes and then press the Add button. If you just set your clients with static IP’s then IPFire will not pick up that those IP’s have been assigned.
Are they showing up in the table named Current fixed leases or in the table named Current dynamic leases?
The Current fixed leases table shows the leases you have defined, whether the involved machines are turned on or not.