Why Doesn't Clock Suspend When Play Suspends

Maybe it´s because the game where running in second plane.

Try going to the task manager and end task.

Quote from: https://community.microsoftcasualgames.com/faqs/can-tell-events/

"There is currently a bug where if you close the window using the “X” button or ALT+F4 during or at the end of an event challenge, you may incur extra time, so make sure you always go back to the event screen or main menu screen before closing the app!

Lots of players have asked about us adding a “stop the clock” button. Unfortunately a “stop the clock” button would defeat the purpose of the competition. If you are not going for a high ranking, time does not matter – you take as much time as you need to
complete the challenges and collect the bracelet awards based on your score. You can also quit the game and come back later which will not count toward your time spent. Only the time you spent playing the Event challenges counts toward your time spent"

It's a product of how a suspended state-app works on the platform. It is a 'feature' that would allow you to quickly resume an app that isn't necessarily the focus or the forefront of your screen, and allows you to resume a title without having to go
through the initial loading screen and pick up where you left off. If you have to leave and don't want to keep the timer running for the app you would have to quit the title completely. Similar to how EA Access's pre-release title tracks time on the Xbox
console. You have to specifically quit the title from the dashboard to ensure that it doesn't use the remaining time when it's not being played and still technically loaded in the background.

You would have to contact the game developers themselves to resolve this. I would also report the bug too

I'm not sure , but i think you cannot stop the game timer.