Timer goes slow problem

I am beginner for making app.

I’d like to make an app for showing second ticks (If user choose 5 minutes and i will show him 300 count down. I’ve used math blocks 560=300. If user choose 1 hour and i change it to 13600 and 3600 sec countdown starts.)
But my timer goes slower than any other samsung phones or laptop clock ticks and its gap between my app timer and other clocks bigger and bigger when i choose bigger time like 30 minutes, 1 hour or more…
I’ve changed millisecond to 970, 960 … but I don’t think it’s a perfect solution.
I’ve read searched about this problem and someone said display delay problem. I don’t get it what it means and how to solve it.

Can anyone help me? Thanks for reading.
(English is not my mother tongue, so I just hope you can understand what i mean.)

Have you seen this post in your search?


yes, but i don’t think it can solve my problem. I’ve downloaded aia file and find out it also has irregular and getting bigger gap.