She made a bunch of calls on the 11th in a row. Some of those calls (made a minute or so from the others) landed on the tower near where her body was found...then the next went to a different tower. So those records show that a call from the home could end up on the tower near where her body was found.
I think the point that's trying to be made is just because if one of the calls made during the morning of the 12th was on the tower close to the body does not automatically indicate that the phone was in that areas