The transmission has a lot more than 5 quarts in it, more like 12 if I remember correctly... the pan itself holds I believe 5. That's why a circulatory flush is the proper way to refresh the fluid on a Subaru automatic.

The way to fill the pan after a drain is to put 3.5 quarts in, then fill progressively until you start to see fluid on the end of the dipstick.

Then start the car, leave it in park, and go through a fill/test routine to bring the fluid level up to Max Cold, assuming the vehicle is cold when this is done, if it is not cold then fill to halfway between Low and Full on the Hot scale. Remember the level can only be measured correctly with the car running and the transmission in Park.

Then drive a few miles to warm everything up, then test again and see if the level is proper... it should be just below or right at Max Hot. Top off as needed.