I didn't find anything in DD or TISA - When we process an interest calculation (due to an error)where a portion or all of the adjustment needs to be posted to the account we are using the overriding description "Interest Adjustment and the start date - end date of the calculation. to process the calculation the start date must be the open date - renewal date- or next day after the last interest payment and the end date is the prior day of the date you are processing the calculation. The true adjustment may be only for a couple of days within the calculation. My question is, should the overriding description read the true adjustment dates or the full month period?

As I recall, TISA and Reg DD don't have restitution provisions like Reg Z does. You simply need to pay what you disclosed. It is probably clearer for the bank and customer if you identify the actual period for which the calculation is made.