On any envelope where the elector's signature and the signature of the attesting witness are required, the signature lines and the signatures shall be across the flap of the envelope to insure the integrity of the ballot and the following shall be printed on the flap on the back of the envelope in bold print and in a distinguishing color: "YOUR VOTE WILL BE REJECTED AND NOT COUNTED IF THIS ENVELOPE IS NOT SIGNED ACROSS THE FLAP OF THIS ENVELOPE BY YOU AND AN ATTESTING WITNESS."