@Anonymous you base rate is just how much your listing costs per night if no other factors change the price.
Some things that can change the price:
- Custom rates
- Weekly / monthly discounts
- Special offers
- Cleaning fees
- Per Guest charges
If you have a single room (that you want to charge a certain amount for),
and you have a twin room (a different room, I assume, that costs a different amount),
then you are supposed to set up two separate listings (assuming you want to allow two different groups to book the two separate rooms.)
If you have two separate rooms but you only want one group to be able to book them... then you have to get creative because there isn't a way to charge per *room*. You can charge per *guest* but that isn't the same thing at all.
What is the setup you are trying to create?