When adjusting entries I have a T Account for Prepaid Office Supplies set up (attached). I need to create an adjusting entry for the Supplies Expense...

When adjusting entries I have a T Account for Prepaid Office Supplies set up (attached). I need to create an adjusting entry for the Supplies Expense (attached as well). My instructor advised me that my answer was incorrect as I originally had a debit of 27,000 to Supplies Expense and a credit of the same to Prepaid Office Supplies. I believe my problem was that I read the mathematical equation instead of actually taking into consideration the 18,000 that was credited in the Prepaid Office Supplies T Account. Would this be accurate?