That is correct, a treasure trove is defined as 10 or more coins. The question is: did the detectorist have permission from the landowner to detect on that land? Did the two of them have an agreement for sharing proceeds? If they didn't have any agreements, their solicitors will be busy.
Saw it could sell for over 600,000. Solicitors get involved lucky to see half.
UK neat play for digging for treasure. Not long ago guy found a part of the crown belonging to Henry VII He found while digging a garden in his back yard. Even mudlarkers find coins from Tutor period right on the banks of the Thames.