45% CDR not properly showing on stat HUD

Playing , using 5% CDR runes, plus Intelligence to allow for 45% CDR cap.

Even after build Trinity Force, Spirit Visage, and Frozen Gauntlet (40% CDR between the three items), my stat HUD is only showing 40% CDR. although I know I have an additional 5% from runes.

I'm just curious if this is a calculation script error on the HUD, an issue with the mastery talent, or an issue with the build itself? Or could there be another issue that I'm not seeing?

Anyway, I just wanted to make Riot aware of this. If for nothing else, an answer to why it's only showing 40% CDR.

Thanks for reading.....