If you look in your uploads folder and see different versions of the same image this is perfectly normal. The theme crops each image to different sizes because these sizes are used in various places on your website. So you may have the same image shown as a 50 x 50 thumbnail and as a large featured image at 800 x 400. The theme will create two additional versions of these images at these dimensions.
This is much more effective than just creating a few different sizes of an image (thumbnail, medium, large), like some themes do, and then resizing them using HTML. If you were to resize a large image with HTML, the large image is still being loaded and then constrained with HTML, which uses more bandwidth and increases your page load time, which in turn is not very SEO friendly. What the theme does is only load the images at the exact size they need to be.
The theme does not currently delete versions of the images no longer in use. So if you change the featured image on your posts from 800 x 400 to 500 x 300 and then to 400 x 600 all of these images will be created but the images no longer used (800 x 400 and 500 x 300) will not be deleted from your server. This is something I hope to add in the future.
You can just leave these images on your server and ignore them because they are not being loaded on your site so they have no impact on your bandwidth or pageload, these just contribute to a bit of disk space.
However you can delete all the resized images in your uploads folders and the server will then only recreate the different image sizes that currently exist on your site. Before doing this first make a backup of your uploads folder and do not delete the original images, only the resized versions that have the extensions -widthxheight.png!