I'm not sure why when you go to buy cooldown reduction runes they say (negative number) ie: glyph is -0.83% it makes it sound like your reducing the percent ie: (you start off with -5% when you really want +5%). Everything else in the game says + for example the mastery sorcery is +5. Please either someone explain it or fix it.
I suppose it could be confusing, but the negative sign simply means that they represent a reduction - as in, a reduction in the cooldowns of your skills.
-0.83% cooldowns
It's worded correctly. Your cooldowns start at 100% (1x time) and you're lowering how long they take down to 60% (3/5x time).
The statistic in game is displayed Cooldown Reduction, which is why it's a number that increases.
If you put CDR runes on a rune page it says (+ -5%) makes nonsense.
Because the runes are old and still works on the old system that used to subtract the CD... somewhere along the way riot ddecided that it would be clearer t be positive up to 40% and changed it and they must have forgotten about the rune tooltip
