Sanhedrin 30: Combined Testimony

When one who borrowed money admitted that he did so - in less formal circumstances than a court, for example, where the claim is that he has set the money aside because he owes it to so-and-so -- that isn't a legal admission. The Gemara provides a general principle when such an admission would count. Also, we follow Rabbi Yehoshua ben Karcha or an admission with regard to land, but not for movable property. [Who's Who? Rabbi Yehoshua ben Karcha] His opinion is also applied for first-born animals which have been blemished and therefore incur a monetary loss. And signs of physical maturity. That is, testimony from 2 witnesses can be combined. But what is the question here, and how was it implemented?