Since you are keeping the same equipment profile and just altering the batch size, you don't need to use the "scale recipe" feature of BeerSmith. Change your finished batch size on the design tab and the recipe should adjust using the same material bill, altering all the parameters of gravity, bitterness, color, and ABV based upon your original grain bill.
Now if you want to make further adjustments, you can click on the sliders below the material box for each of the calculated parameters and enter in the new target. BeerSmith will adjust the recipe accordingly to match your new target by altering the grain bill or hop additions proportionally to match your new target.
Note that this assumes that you will hit the same brew house efficiency with a lower batch size. While this is possible, you will need to take careful measurements and record what your actual brew house and mash efficiency are with your reduced batch size so that if you choose to do this again, you can make those adjustments. Better yet, you can then develop a new equipment profile to take into account your new batch size and efficiency so that you can then use the scale recipe tool to make these changes for you.