6. The terms on which the operator invites persons to bet by means of the totalisator may include a condition entitling the operator to retain any sum payable to a person winning a bet unless the money won on the bet is claimed before such time, not being earlier than 48 hours after the conclusion of the race, or as the case may be, of the last of the races, in connection with which the bet was made as may have been specified in the notice posted in pursuance of paragraph 3.N.I.