Hot really mate. You should take into consideration the monthly and weekly discounts given.
Say you're offering your room for $100 per night, 30 days that is $3000. But if you offer a 20% monthly discount your monthly price is actually 2400. The way the system works is it takes into account all these discounts and spreads the price over the entire period. That is why it will show as the new price $2400 / 30 nights = $80 per night to the guest
That means that the customer originally saw $80 out of your original $100. But without the discounts the system takes the full price. You could if you want to adjust it to the original agreement, or just explain where the difference comes from. You're not cheating them, but it's also fair that they don't understand.
This is also the deal with differentiated pricing based on day of the week. If for example you charge $50 on a weekday and $100 on a weekend, somebody that comes for Thu and Fri will see a price of 75$. If you cancel one night you're in for a suprise. A good one or a nasty one.