I finally tried some of the dehydrated hash brown tonight.
Here is what I did and it worked great on the first try.
1/2 cup hash browns
1/3 cup of water
Pour water over hash browns and let set for 15 minutes.
I did one batch and my husband said that it wasn't enough for just him. I did the same thing again. I used cold water on the first batch and warm on the second batch. I didn't make any difference. It still took 15 minutes for the water to absorb. The first batch actually sat for about an hour before he got home.
I mixed the two together and fried them like I do fresh grated potatoes.
I wish I had measured them after they were rehydrated, but I forgot.