Adjustment:

One month’s advertising was expended in accordance with the agreement made
With the newspaper on December 1.

November Advertising Expense: $300.00
December Advertising Expense: $200.00

Will it show Advertising Expense only $200.00 and consider December Advertising Expense as expended

OR

Total expended: $500.00

What $$ amount will be reduced or increased during adjustments

I don't know what month you're trying to do the entries for. The information is confusing. Even that first sentence: does that mean the agreement was made on Dec 1 or that one month had been expended by Dec 1? And I don't know if you're trying to do an entry for Nov 30 or Dec 31.

Can you clarify the information?