Portion Size sets the portion every meal in the pack is served in; the dropdown offers a fallback "default portion" option (its label comes from an internal setting that is not currently exposed as an editable field on the Client Config page) plus your active meal-prep portion sizes. On the website a pack is listed only if it is Active and its portion size is still active — a pack tied to a deactivated portion size is skipped silently. Packs cannot be deleted; switch Is Active? off to retire one, which removes it from the website and shows Inactive in the list.