If the Subpod is in a raised garden bed, the immediate area (half a foot or 15 cm) around the Subpod will be enriched quickly (within several months).
For a single Subpod, this will work well for a raised garden bed of about 3 feet/90 cm by 5 feet/150 cm. A garden bed smaller than this will simply be enriched faster. If your garden bed is larger, you have the option of adding an additional Subpod(s) or simply letting it take longer to enrich the garden bed.
The minimum bed for composting would be about 45 inches/110 cm long by 30 inches/ 80 cm wide, however a larger bed would also allow food to be grown in it as well.