Bava Batra 107B

תשעין שויא; והאי דקאמר עשרים, דקא טעי עשרה לאחוריה; והאי דקא אמר מנה, קא טעי עשרה לקמיה.

is in fact worth 90 dinars, and the one who says it is worth 20 sela, which is equivalent to 80 dinars errs with an assessment that is 10 dinars behind, i.e., too low, and the one who says it is worth 100 dinars errs with an assessment that is 10 dinars ahead, i.e., too high. Therefore, the average of these two assessments is followed.

אדרבה! האי ארעא מאה ועשרה שויא; והאי דקאמר מנה ⁠– קא טעי עשרה לאחוריה, והאי דקאמר שלשים ⁠– קא טעי עשרה לקמיה! נקוט מיהת תרי קמאי בידך, דמתורת מנה לא מפקי ליה.

The Talmud raises a difficulty: On the contrary, say that this land is in fact worth 110 dinars, and the one who says it is worth 100 dinars errs with an assessment that is 10 dinars behind, and the one who says it is worth 30 sela, which is equivalent to 120 dinars, errs with an assessment that is 10 dinars ahead. If so, the average of these two assessments, 110 dinars, should be followed. The Talmud replies: In any event, grasp the first two assessments in your hand, as neither of them takes the assessment beyond the sum of 100 dinars.

אחרים אומרים: עושין שומא ביניהן, ומשלשין ⁠– קא סברי: האי ארעא ⁠– תשעין ותלתא ותילתא שויא; האי דקא אמר עשרים ⁠– קא טעי תליסר ותילתא לאחוריה, והאי דקאמר מנה ⁠– קא טעי תליסר ותילתא לקמיה; ובדין הוא דלימא טפי, והאי דלא קאמר, סבר: מיסתאי דקא מטפינא כולי האי אחבראי.

The baraita teaches that Aḥerim say that an appraisal is performed of the sum between the two most extreme assessments and then divided by 3. This sum is then added to the lowest assessment. The Talmud explains this opinion: Aḥerim hold that this land is in fact worth 93⅓ dinars. The one who says it is worth 20 sela, the equivalent of 80 dinars, errs with an assessment that is 13 dinars and 1/3rd behind, and the one who says it is worth 100 dinars errs with an assessment that is 13 dinars and 1/3rd ahead. By right, that assessor should have said more, i.e., quoted a higher sum, since according to this calculation, he should have said it is worth 106⅔ dinars. And the reason that he did not do so is that he thinks as follows: It is enough that I add this much above and beyond the assessment of my colleague who says it is worth 80 dinars. Therefore, he lowers the sum of his assessment to 100 dinars.