Thanks. It says add 1/4 of the packet to an 8 litre watering can. Ah, it says you can repeat the process another 3 times (fills 4 watering cans), but each can load only treats 1/4 of the 50 sq yard area.
So 8 litres of solution treats 12 sq yards of soil (I think)
Sorry, my Maths never was...