If I have am completing an adjustment journal, and I have purchased $1,600 in supplies, but only have $400 of those supplies on-hand, how would this be properly represented in a general journal? The applicable account titles would be supply expense and supply.

I am pretty sure I would list supply expense debit 1600 and supply credit 1600, but this does not account for only having $400 worth on hand at month-end. Would the credit only be $400?

Thank you in advance for any assistance.

The entry to record the purchase will be:
Debit Supplies for 1,600
Credit Cash for 1,600

To record the adjustment you have to get your account balance of $1,600 worth of supplies into agreement with your actual physical balance of $400 worth of supplies. So your adjusting entry will be:
Debit Supplies Expense for 1,200
Credit Supplies for 1,200

This transaction moves $1,200 worth of supplies out of your Supplies account balance and expenses them in the period that the supplies were used leaving you with $400 worth of supplies remaining in your account balance, which is the same balance as your physical account balance.

Thank you. I'm catching on to this, but I am wondering. Let's say it were a slightly different scenario. What if I paid $1600 for supplies but did not receive any of the supplies until the following period. Would this constitute a debit entry of $1600, and a credit entry of $1600 in the general journal, but then no entry in the adjustment journal?

Thank you.

Your Debit would be to a receivable account (like Supplies Receivable) for 1,600 and your credit would be to Cash for 1,600

You would do an adjustment to bring your Supplies account balance into agreement with a physical count balance (usually at the end of an accounting period).