Disambiguation of "Let me know when the task is completed."

Question

The sentence "Let me know when the task is completed." could have two meanings:

1. Let me know the time that the task is supposed to be completed.
2. Once the task is completed, let me know it.

Which of them makes more sense?

Answer 1

I don't agree that there is any ambiguity. The sentence

Let me know when the task is completed.

has your second meaning

Once the task is completed, let me know [it].

If you want to be told when the task is supposed to be finished, I suggest

Let me know when the task will be completed.