Imagine you have 3 apples in a box.

Remove one apple from the box, how many remain in the box?

Two. Simple. Right?

Remove one more. One remains.

What if you remove the last apple from the box.

How many apples remain in the box?

Well, it should be zero apples right?

Well the answer is not that straightforward.

Think about it.

Just smell the box.

Does it still smell like apples?

Ofcourse.

The scent of apples remains in the box.

Well, that means that there's still a TRACE of apple remaining in the box. This contradicts the fact that the number of apples in the box remaining is absolute zero.

Infact if you think about it, it can never truly be absolute zero. There's always going to be a trace of apples remaining in the box no matter how careful we are at handling them.