Purposely left plot points (spoilers) out of the post title.
Im not sure but i did count his markings on that paper when he was trying to get a signal. I counted 17 x 5 so im guessing nearly 3 months.. He had a good set up which would have took time, and he was very organised.
That's what I figured from his marks--a few months.
We don't know, and that did not bother me. This was a very lean film, and I enjoyed it. 😎