This means that op.profit of STN was 29% of the total, for 40% of the pax. Even worse for MAG, as they have to service their debts from the op. profit.
Why is that so surprising? STN is "Farmfoods" whereas MAN is more akin to "Sainburys". One piles it high and sells it cheap and has a small range of products, the other has broader range of higher quality (profit) products.
MAG are probably quite happy with the mix within their business.