For those not named Capasse...
From Oswald's position having just turned the corner from Tenth onto Patton, Guinyard was halfway down the block and Callaway was three-fourths of the way down the block, i.e. Guinyard was closer to Oswald at that point. Both Guinyard and Callaway were standing on the sidewalk on the east side of Patton.
Oswald, as he is heading down Patton on the east side, sees these two men further down. As Oswald is nearing Guinyard and not running to run right past him within mere feet, Oswald crosses over to the west side of the street. Oswald is now across the street from Guinyard.
Oswald continues down Patton on the west side and shortly before reaching Jefferson, he is now directly across the street from Callaway. This is where the fifty-six feet distance comes into play.