Actually, level 8's are built so that you are supposed to end with 100% every time. So if you got 82%, that would be a bug. I will look into that and see what I find. Thank you for pointing it out!
Also, since the level 8 design is randomized, the next time you do the level, it'll have a different layout and may allow you to get 100%. So if you try it again, you can unlock the permanent color aura for yellow. 👍🏻
Edit: I just looked into it, and I was able to find the bug. It'll be fixed in the next upload. Sorry about that. 🤦🏻♂️