Scaling CD Reduction Rune Flaw!

Hey, I recently was managing my Rune page. Had my 6 Scaling CD Reduction Runes ready to get me that 10,02 CD Reduction. I had previously figured out that 6 Scaling CD Reduction Runes would get me -10,02 CD Reduction at lvl 18. Using a calculator. If you take 1,67 and multiply it by 6, you get 10,02. But it says I only get 9,7. ( It says you get -1,67% at lvl 18 per rune ) This is because it says you get 0,09 cd per lvl which equals 1,62, NOT 1,67. 0,09 ( cd per lvl ) X 18 ( max lvl ) = 1,62 ( cd per rune at max lvl, which game says should be 1,67 ) x 6 ( amount of runes ) = 9,72 You can see the conflicting values here.

Screenshot is provided in the discord link, I dont post screenshots often, couldnt bother linking it somewhere else.