Help with Chronometer App

I have created an app that is a Chronometer, my app works perfect but two of my student's apps at the start, the app shows some numbers, if they click the start button the numbers are gone but at the beginning, they are there, I had reviewed all the blocks but I cannot find what the problem is, can you help me

Emulator

ChronometerAlexDiaz.aia (27.6 KB)

Ask yourself,
what is the duration between 0 and Now()?

That's what you see at startup.

TimeEnabled

The millisecond 0 happened way back in 1970.
If you don't want to see how many milliseconds have elapsed from 1970 to Now(), don't show the Duration. Keep the label invisible until you hit the Start button.
Alternatively, assign Now() into global Start in Screen1.Initialize.

Further thoughts ...
Look in the Designer at the Enabled and RRepeating flags for Clock1.
Did you leave them both enabled?
Bad idea for a stop watch.
You want to enable the Clock Timer in the Start button, not leave it to run before you hit the Start button.
Set Clock1 Enabled False in the Designer.