פירוש על קידושין 120:17

A “bet kor” is the amount of land it takes to grow a kor of produce. In modern terms it is about 17,000 sq. meters, a rather large piece of land. This clause is nearly the same as the end of the previous mishnah.

Land value differs from place to place. It seems here that the woman wants to know that he owns good land, and not a worthless piece of land.

This is nearly the same as the final section of the previous mishnah. Showing it to her in “the plain” means that he shows her land that is not his. This is not what she thought he meant by his “showing her a bet kor.”