VLAN on r7800 tagged or untagged on eth1

Installing and Using OpenWrt Network and Wireless Configuration
3

I do not fully understand, but if it makes sense, ok.
the sample over here is also without .x

config interface 'lan'
        option proto 'static'
        option ipaddr '192.168.1.1'
        option netmask '255.255.255.0'
        option ip6assign '60'
        option device 'br-lan'

config interface 'wan'
        option proto 'dhcp'
        option peerdns '0'
        list dns '127.0.0.1'
        option device 'eth0'

config interface 'wan6'
        option proto 'dhcpv6'
        option reqaddress 'try'
        option reqprefix 'auto'
        option peerdns '0'
        list dns '0::1'
        option device 'eth0'

config switch
        option name 'switch0'
        option reset '1'
        option enable_vlan '1'

config switch_vlan
        option device 'switch0'
        option vlan '1'
        option vid '1'
        option ports '1 2 3 6'

config switch_vlan
        option device 'switch0'
        option vlan '2'
        option vid '2'
        option ports '0 5'

config switch_vlan
        option device 'switch0'
        option vlan '3'
        option ports '4 6t'
        option vid '9'

config device
        option name 'br-lan'
        option type 'bridge'
        list ports 'eth1'

config device 'guest_dev'
        option type 'bridge'
        option name 'br-guest'
        list ports 'eth1.9'

config interface 'guest'
        option proto 'static'
        option device 'br-guest'
        option netmask '255.255.255.0'
        option ipaddr '192.168.5.1'