"All and each of the grantees children, heirs, posterity, and descendants of either sex, born or to be born, for ever."
Under the terms of this unique document anyone legally descended from Thomas Arundell is a Count or Countess of the Holy Roman Empire.
You could be an heir. There are many families in Europe, the U.S.A., Canada, Australia and New Zealand who can claim descent from Thomas Arundell and can legally claim to be a COUNT or COUNTESS and be entitled to a family COAT OF ARMS.
Check your family names in the list.