1. I is for regular Inventory. You will hear notifications on items that are checked out to system patrons that should not be book-dropped. 
2. IB is for Inventory Bookdrop. You will hear notifications on items that are checked out to system patrons that should be book-dropped. 
3. IBS is for Inventory Bookdrop Suppressed. You will NOT hear notifications on items that are checked out to system patrons, and should be book-dropped.
4. IS is for Inventory Supporessed. You will NOT hear notifications on items that are checked out to system patrons, and should NOT be book-dropped.

To forgive a charge for an individual patron, use Circulation.

1.  Make the patron current and go to the Charges tab. 
2. Select the charge (or by holding <shift> or <command> you can select more than one). 
3. Click Make Payment.
4. Enter the amount to forgive in the forgive field, and click Process. 

To forgive charges in batches, use the Forgive Charges utility. 

1. Go to Tools > Utilities > Patrons > Forgive Charges.
2. Use the Selections tab to choose who you are forgiving the charges for.
3. Use the Options tab for what type of charges to forgive, or in a specific date range. 
4. Click Run