Thanks for sharing your file, Seth!
The overall size of your published course is a little bigger than your slide dimensions, and the player adds up to 260 pixels to the width and up to 118 pixels to the height, depending on the player features you selected. You can find more information about how the dimensions are configured here.
If you’re looking to remove the border, you might consider hiding the player features to create a chromeless design or creating an invisible player (this option is specific to the Classic Player).