We are learning chapter 4, mishnah 9. This mishnah is a direct continuation of the previous one, and its explanation was already included in the explanation of the previous mishnah that was learned together with it - it contains no new principles, only a practical illustration of the rules that were already explained.
The text of the mishnah and its explanation:
"Keitzad" - How so? The mishnah now comes to illustrate the points that were explained, showing how Rabbi Akiva rules in such a case.
"Chamishim te'enim shechorot vachamishim levanot" - Fifty dark figs and fifty light figs are lying in a vessel. From here three cases emerge:
"Naflah shechorah - shechorot asurot vehalevanot mutarot" - If it was seen that a dark fig fell in among them, the fifty-one dark figs are forbidden to be eaten as a medumah mixture, and he must give them all to a kohen for the price of one less than the amount he had in hand, that is, fifty. The light ones, however, are permitted - he separates them out and eats them, and there is no problem with that.
"Naflah levanah - levanot asurot ushechorot mutarot" - And so too the reverse: if a white fig fell in, the fifty-one white figs are forbidden as a medumah mixture, and the black ones are permitted to be eaten.
"B'she'eino yodea mah naflah - ma'alot zo et zo" - If he saw a fig fall but did not notice whether it was white or black, the black figs and the white figs combine with one another to make up the count of a hundred, so as to complete a mixture of one hundred and one, which is permitted to be eaten.
"Uvazo Rabbi Eliezer machmir v'Rabbi Yehoshua meikel":
One should not be confused by this last statement, which is of no great consequence at this point. The mishnah is simply pointing out that in this case Rabbi Eliezer is the one who is stringent, while Rabbi Yehoshua is the one who is lenient - for he is the one who said that one may be lenient in the way the hundred is reached. There is no new information here at all.
The mishnah brings this in order to set up its words against the mishnah that follows.