It depends on the type of seed and the seeding rate. There should have been a manual that came with the spreader. If you don't have it, see the earthway website below. Find your spreader and click on it even though you are not buying it. When it goes to that page, there is a grey tab for the manual for that particular spreader.
If you have troubles finding the manual, let me know your model number and I can try to find it.