With Router OS you can do VLAN in many ways. Just look at my post trying to learn VLAN here:
http://forum.mikrotik.com/t/sofware-vlan-bridge-on-ruteros-explained/122534/1
You need to see what is going on here. Think of this as two devices.
Side on, the Interface. You need to tell the interface site what is the untagged vlan
/interface bridge port
add bridge=bridge1 interface=ether2 hw=yes pvid=20
Side two the Bridge. Here you need to tell how VLAN is handled against each interface.
/interface bridge vlan
add bridge=bridge1 tagged=ether1 untagged=ether2,ether3 vlan-ids=20,30
I do agree its very confusing and complicated.