At the beginning, when Micah walks out of the saloon- in the window you can see Lucas and Mark sitting on their horse. They are waiting on their cue, which happens right after Micah leaves, to come riding up in the scene.
The note Lucas leaves for Mark takes up 3/4 of the page, but it is less than 1/2 of the page when Carl reads it. The note Carl leaves is less than 1/2 of the page, but is 3/4 of the page when Micah finds it.
At the very beginning as Micah walks out of the saloon, through the window you can see Lucas and Mark waiting on their horses at the edge of the set for their cue to walk in.