Most likely, "21" refers to a volume number or a model index. Many niche content producers (often using storefronts like Clips4Sale or ManyVids) serialize their work. "Loon Elevator 21" suggests this is the 21st installment in a long-running series. It implies a certain production quality—the creator has made 20 previous successful elevators, so "21" likely contains advanced techniques, larger balloons, or higher risk.
The "elevator" setting mentioned in the query highlights the importance of "situational" content. In various hobbyist circles, the environment in which an activity takes place is as significant as the activity itself. An elevator provides a controlled, minimalist backdrop that emphasizes the focus on the primary subject—in this case, the balloons. The confined space and the metallic aesthetic provide a specific visual contrast to the organic, colorful nature of the latex. Digital Evolution and Community Archiving looner balloon fetish loon elevator 21 30clips upd
For the archivist, the "30clips upd" is a timestamp—a mark of curation in a flooded digital sea. Most likely, "21" refers to a volume number or a model index