Do you want to change the nightly pricing of the rooms like giving a discount or adding a mark up or just adjusting the total amount of the reservation for just any reason?
You can actually change the pricing of the rooms per night for each reservation.
1.) Go to the reservation you want to change the price.
2.) Click on Room Breakdown under reservation details.
3.) Change the room rates according to the date of the reservation.
While you can adjust the total amount of the reservation by using the price adjustment function. You can use this feature when you want to add a specific increase or decrease in the total amount, like when a guest lost the room key and etc.