beginner - kind of okay but odd; minute-seconds timer

[Joe]

Hello,
Beginner question here.
Script attached gives strange results; kind of okay, but ...odd.
It's a minute-timer seconds-counter and it works pretty well but I do get some strange results.
The script asks the user for input in minutes (digital), so you put in .5 or whatever.
A second hand sweeps around clockwise (once per minute) while a counter displays the passing seconds in tenths.
If I request .25 minutes, the readout is 15.1 second. Not too bad, but still wrong.
All is fine from there up to .85 (actually .844) minutes.
At that point the counter displays 9 more empty decimal places…?

Any thoughts about why ?
attached: clock_minsecTimer2.py