Changes

Create a rate and set “Offer” in the “Rooms” tab to the offer number you set to “internal”

Go to SETTINGS->PROPERTIES->ROOMS->DAILY PRICES and set “Offer” of the daily price you want to use internally to to offer number you have set to “Internal”. When you go to the CALENDAR you will see a new daily price row where you can set the internal price.

After you have set this up you can select this offer when you add a new booking.