How volume is counted
Volume here is the number of working sets a muscle gets in a week. Not reps and not tonnage: sets taken close to failure are what the research on muscle growth counts, and it is the unit a plan is written in. Warm-up sets do not count.
Each exercise has a primary muscle and often secondary ones. The primary muscle gets a full set, each secondary muscle gets half. For example, bench press, 8 sets: chest 8, triceps 4, front delts 4. Half a set is the convention used in volume research and by Renaissance Periodization, because a secondary muscle works but is not the one that limits the set.
Ranges by muscle
The lower number is roughly where a muscle starts to grow, the upper one is the edge of productive volume: past it, recovery usually stops keeping up. The ranges follow Renaissance Periodization's volume landmarks and are the same ones the Steelheft app uses: Quads 8–18, Hamstrings 6–16, Glutes 4–14, Adductors 4–12, Calves 8–16, Chest 10–20, Lats 10–20, Upper back 8–18, Traps 4–14, Lower back 2–8, Front delts 4–12, Side delts 8–20, Rear delts 6–16, Biceps 8–18, Triceps 6–14, Forearms 4–14, Abs 6–16, Obliques 4–12.
Front delts have a low range because presses already give them half sets; the same goes for triceps from presses and biceps from rows and pulldowns.
The same count in the app
Steelheft counts weekly sets per muscle the same way for the plan and for the sets you log, colours the muscle map by it and tells you when a set moves a muscle into its range or past the top of it.