Top off to one gallon if this was an extract brew. Your boil off rate is high. This can be caused by to vigorous of a boil, or a kettle with an overly large surface area/diameter for the volume being boiled.
Welcome to home brewing and everything that goes with it. Sprinkling dry yeast on the wort can kill half the yeast. For low gravity beers this is not a problem, there is still sufficient yeast for a good fermentation. Some instructions say to use it dry because rehydrating the yeast may be to complicated for beginning brewers.
It is very simple to rehydrate dry yeast. Sprinkle the yeast on top of water, where the volume of water is equal to ten times the weight of the yeast. 11 grams of yeast would be sprinkled on 110 milliliters of water, four ounces of water. Water temp would be 85°F to 95°F. Let sit for 15 minutes, then stir the yeast in. Let sit another 15 minutes before pitching. The rehydration process should not exceed 30 minutes or the yeast could begin using up their built in reserves. Do not use reverse osmosis water or distilled water. Private well water or bottled water is best. The water needs some mineral content to protect the cell walls of the yeast from being damaged.
Go to the yeast manufacturers site for the optimum fermentation temperature to preven off flavors from a to hot fermentation. Optimum fermentation temperature is usually in the low 60°F range. (US-05 and WY1056 are best at 65°F to 68°F.) Temperature control is critical in the fist few days of active fermentation. A swamp cooler can be used to keep the beer from getting to warm.
Not wanting to get in an argument here but I never have rehydrated a packet of dry yeast with one exception. Just as an experiment I used two packets of Safale us-05 in two carboys from the same 20 gallon batch. One I followed the instruction on how to rehydrate and added it, the other simply sprinkled it in. The result was you could not tell any difference. Gravity readings were identical in OG and FG. This is my personal experience YMMV.