Entrances and formation are already set
The scene already contains the entrances, the spacing, the camera, and the background behind the line. You are not staging a new floor or deciding when each figure walks in. Photo 1, Photo 2, and Photo 3 step into places the performance has already marked.
A photo taken on a beach does not move the dance onto sand. The formation stays. If you want another location, another count of figures, or a routine this clip does not contain, open /video and describe that routine there.
Three slots, and no fourth role
Three slots means three assignments. There is no upload for a soloist who is separate from the left figure, because the opening figure is Photo 1. There is no slot for someone behind the line. Adding another face inside one photo does not create a supported role. Repeating one file across slots still uses only those three places.
The result runs about 12 seconds, following the dance that is already there. You cannot extend the number, insert a new entrance, or hold the ending. Watch from the opening figure through the last formation. Duration is part of the scene, not a setting.