clear pentakill denials

so i've been playing league of legends for 3 years now and i've realised that if you get a quadra kill u can delay the penta for as much as 30+ seconds, meanwhile i just got a triple kill and some 5-10 seconds later i killed the remaining 2 enemy players thus scoring the ace but instead of getting a pentakill i got a double kill, this has denied me so many pentakills and i want it to be changed