It was a charge registered against OUFC, not the owners. It meant that any revenue was redirected into a holding account and had to be paid to Ensco 1070 Ltd. (wholly owned by D Eales) It was set up for the outstanding amounts from player sales. It was not part of the purchase it was simply a vehicle for Ol' Slippery to walk away in profit when, in reality those player sales should have benefitted the club. Despite all his promises to see the club debt free, Eales still left the club shackled. He even retained voting rights through shares long after he had departed. That voting right meant that he could check on the payments and make sure he didn't miss anything.
The charge is registered at Companies house
Here This "charge" over OUFC was eventually settled.