CDR info

The bottom left shows all the stats of your champion, how much ad you have, how much ap, your defenses and many things but i always see my CDR almost always read out to 45% if i have the the mastery point in play. Even when i should only have 15% cdr having only cdr from 1 item and 5 from the mastery somewhere along the lines i see it changes it to 45% im not sure if its bug from the mastery or if the 10% from blue buff stacks and doesnt lower when you lose the buff. If im paying attention to my items its not a big deal because i know how much cdr the items give but if i rather quickly glance ill end up changing my build due to misinformation from the stats portion. I dont pay attention to it on every champion but i only ever see this happen with people that use the 5% added to max cdr mastery.