Suncast storage shed

I just purchased this 6x4x6 shed thinking it would be enough for all of my work supplies but apparently I have more than I was expecting. I already put it together and threw away the box so I cant return it. Just set up last week. Actual dimensions are 5' 10-1/2" W x 3' 8-1/4" D x 6' 5-1/2" H. Paid $400 plus tax. Asking $275