CDR increasing ability ?

Was playing Syndra and had 45% CDR (Mastery, Blue buff, Morello, Abyssal) Middle of getting bursted i notice i have 15% CDR My ult went on 1:05 seconds (appx.) cooldown, but when i hovered over it, it shouldve taken around <55 seconds

enemy team had: , , . , ekko, cassiopia, ashe, vayne, ryze

just a heads up