Is it possible for a 13yr old to run a 4.3 sec on a 40yd dash?I ran a 4.3 but used a iPhone to time?

I am 13 and ran a 4.3 but I looked up the nfl runningbacks roster and they got higher times such as 4.5 or 4.4.... I work hard to get my 40. time lower and use a sled.....
I used my iPhone to time myself.. maybe that Is the case?