In Predator 2, the Yautja is seen enabling the explosive device, as he think the fall is imminent; then Lieutenant Mike Harrigan, slashed the right arm of the Predator, with the device embed to,causing the alien fall and use the blades as support to broke thru a window.

But if the clock was already running, why the device didn't exploded?

In Predator 2, the Yautja is seen enabling the explosive device, as he thinks the fall is imminent; then Lieutenant Mike Harrigan, slashed the right arm of the Predator, with the device embedded, causing the alien to fall and use the blades as support to break through a window.

But if the clock was already running, why didn't the device explode?