12. An authorised officer may not determine the seed potatoes as meeting the requirements of Union grade S, SE or, as the case may be, E if, in relation to the immediately succeeding crop produced from those potatoes, the number of growing plants which—
(a)deviate from variety, is likely to exceed 0.1% of the total number of plants in that crop;
(b)deviate from variety and type, is likely to exceed 0.25% of that total number; or
(c)show symptoms of any virus attributable to infection in the mother crop, is likely to exceed 4% of that total number.