Misc files are what the wizard has used and also bits left over from app updates and files.
If you clear data normally this should go, but then you need to re-run the wizard again in Kodi.
You can also go to Apps in the main android boot menu (dot with six circles or My Apps), and here go to ES File Explorer and go to the side menu and click on Tools. Now click on the SD Card Analyst, let it run.
After its finished you can see how your memory been used up, and the biggest one at the top you can click on this until you see files you don't need and delete them. Then go back and go to recycle bin and empty it.
Theres is more on this on another thread by SilentlyScreaming check it out.