pfSense

The interfaces list shown in the console will show a subnet value from the config file if it is present for a DHCP configured interface.
The config file value is not actually used by a DHCP interface which receives the subnet via DHCP. This does not affect function of the interface, the console just shows an incorrect value.
It will show any configured there. For example:

        <wan>
            <enable></enable>
            <if>mvneta0.4090</if>
            <ipaddr>dhcp</ipaddr>
            <ipaddrv6>dhcp6</ipaddrv6>
            <subnet>64</subnet>
            <gateway></gateway>
            <media></media>
            <mediaopt></mediaopt>
            <dhcp6-duid></dhcp6-duid>
            <dhcp6-ia-pd-len>0</dhcp6-ia-pd-len>
            <switchif>switch0.port3</switchif>
        </wan>

[2.4.5-RELEASE][admin@1100-2.stevew.lan]/root: ifconfig mvneta0.4090
mvneta0.4090: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
    options=3<RXCSUM,TXCSUM>
    ether f0:ad:4e:08:6b:df
    inet6 fe80::f2ad:4eff:fe08:6bdf%mvneta0.4090 prefixlen 64 scopeid 0xa
    inet 172.21.16.219 netmask 0xffffff00 broadcast 172.21.16.255
    groups: vlan
    vlan: 4090 vlanpcp: 0 parent interface: mvneta0
    media: Ethernet 1000baseT <full-duplex>
    status: active
    nd6 options=23<PERFORMNUD,ACCEPT_RTADV,AUTO_LINKLOCAL>

*** Welcome to pfSense 2.4.5-RELEASE-p1 (arm64) on 1100-2 ***

 WAN (wan)       -> mvneta0.4090 -> v4/DHCP4: 172.21.16.219/64
 LAN (lan)       -> mvneta0.4091 -> v4: 192.168.219.1/24
 OPT (opt1)      -> mvneta0.4092 ->