(7)Where the deponent is illiterate, blind or unacquainted with the language in which the affidavit is written, a certificate by the person before whom the affidavit is sworn to, the effect that the affidavit was read, translated or explained in his presence to the deponent, and the deponent seemed perfectly to understand it and has signed the affidavit or affixed his mark in his presence, shall be attached at the end of the affidavit.
