Is this a lot of bird (1 Viewer)

I buy kaytee basic blend wild bird food seeds but sometimes they can finish the food in less than 12 hours, actually they always eat all of it by then and I have a perky pet bird feeder that holds 2lbs of bird seeds. Is this enough for 1 day? I only fill it up 1 time most days. If I fill it up 2 times then they will eat 1 and a half. I am just trying to make the food last longer. I just bought two 20lbs bags. I dont have a problem with buying food but should I also be leaving 8oz cup of seeds on the grass for the bigger birda since some of them are too big for the bird feeder. I only do this a few times. I just let them eat the food that was dropped from when the smaller birds are eating from the feeder.