Your hydrometer should be calibrated for 1.000 at 60F (I know, some are 59F).
Let's assume your hydrometer is correct. Your OG was 1.045 and your temp was 76-78F. Firstly you have to correct the reading by adding 3 points (0.003 actually) raising it to 1.048.
This is closer to the gravity recommended by the recipe, but another factor is the amount of water. Was it 5 gals? If it was 5.5 gals then the sugars would be more diluted and give you a lower reading...less water a higher reading.
This is one reason why some brewers who care about hitting the exact gravities will not fill to 5 gals right off. They will fill up to 4.5 gals then take a gravity reading. If the projected gravity is still a couple of points off they will add a bit more water until the gravity is met regardless if the volume is 5 gals or not.
Check the calibration of your hydrometer and go from there.