It shows a couple things.
1. Homicide detectives subpoena'd Fred Murray's cell phone records.
2. They were asking for a CDR, which means "call detail report," meaning records of calls going in and out.
4. The search parameters (Feb 1 - Feb 20) suggests they believed possible criminal activity was happening beyond the time of Maura's disappearance.
This document was part of the items released to Fred by the Supreme Court of New Hampshire and can be obtained through FOIA.
A few readers have pointed out that a subpoena to a phone company may be standard procedure in order to maintain chain-of-custody. Also, these records may have been a way to alibi Fred out.
As I've said before, I do not believe Fred is responsible for Maura's homicide (if that's what it is). But I do believe he knows what led her to drive into New Hampshire. And, to me, that is half of the puzzle in this case.