Morrisons pregnancy tests

Yesterday I got a very very faint line (see below) with a Morrisons test. I tried again today with a clear blue and nothing, the detection limit is 25mg on the clear blue. Does anyone have the instructions for the Morrisons tests and know what levels they detect from? I thought it was too good to be true when I got the very very faint line! I'm not due on my period until Friday so it's still early!