If its your last VAC period of the year, you can reduce the "footprint" down to the amount of VAC you have left, ie, 12hrs left, 2 day footprint of VAC days, vice 7 (or however many).

7.G.4. If the SCH value of a pilot's last vacation period in a year exceeds the balance in his vacation credit hour bank, he may elect to reduce the number of vacation days in his vacation period in order to avoid or reduce a deficit in his vacation bank. A pilot shall communicate this election to CRS during the Conflict Input Window.