Some advice wrote:
It is physically impossible to run on your toes not forefoot, given your height and weight.
Even if the timer itself is perfectly accurate, the display could conceivably change from 11 to 12 at 11.5 seconds, or 11.99999 seconds based on how it is programmed, so you may have run anywhere between 10.50 and 11.99 to see 11 on the app, which is the difference between a scholarship level high school sprinter, and a JV scrub.
Wrong. He can run on his toes.
You are right that this is not a good estimate of time, though. OP, get in a timed race or even ask someone, preferably a coach or runner, to time you with a watch that actually has tenths of a second. THEY say "go" and THEY stop the watch.
Honestly, let us know what you get!