What you really need is two scripts. What you’ve got there is primarily useful if you’re looking for a way to present a timer visually to the player.
To make a timer that would end the level after 10 minutes, you actually need a much less complicated graph.
For example, Using the Event “BeginPlay” you would then add a “Delay” and set it’s duration 600 seconds, which would be 10 minutes, and then you can execute whatever actions you wish to take to end the level, you could use a branch node to have the end event be different in certain conditions were met before the timer ran out.
For a visible counter that counts down you’ll need to turn that addition into subtraction, and basically inverting the entire clock. Instead of counting up to 60 seconds and then increasing the minutes, you would count down to 0 seconds and then decrease the minutes and continue counting down.