WordPress resizes the images when you upload them based on the settings in the functions file in your active theme. If you switch themes it might resize everything again leading to the many sizes, butI’m not sure if that is why you have so many strange sizes.
This is the wordpress page related to the deprecated image function, and this is the newer instruction.
Your theme mentions something about this as well.
Important Note: The WordPress thumbnail function re-sizes the image you upload based on what thumbnail sizes are needed for your theme. Each time you change a theme, you may need to re-generate these thumbnails so that they fit your new theme correctly. You can use the Regenerate Thumbnails plugin each time you switch themes to re-generate your thumbnails. After enabling this theme, you should run this plugin to update all of your old thumbnails to avoid design inconsistencies.
Hope that helps you find the answer.