The Little I Know,
“הקובע מקום לתפלתו אלקי אברהם העזרו. What is meant by קובע מקום is discussed by the poskim, whether it means the same shul or the exact spot in that shul.”
Well, the Mishnah Brurah says that it means the man’s seat in shul, but that anywhere he sits within daled amos of his seat is still his makom kivua.