What is the meaning of "mi'Hyosam Ba El Aremas Esrim"?
Rashi: Instead of having a curse in your deeds, like until now, that they made a stack proper to measure 20 Sa'im, and they measure only 10.
Radak: They can recognize that it is from Me. The stack should have 20 - why does it measure only 10? It is a curse from Me!
What is the "Yekev"?
Rashi: It is the pit in front of the winepress. The wine descends into it.
What is the meaning of "Lachsof Chamishim Purah"?
Rashi: To draw from it 50 measures into which they measure wine in winepresses; it is called Purah. Lachsof is to fill, like "v'Lachsof Mayim mi'Geve" (Yeshayah 30:14).
Radak: Lachsof is to take or draw, like "v'Lachsof Mayim mi'Geve." Purah is like "Purah Darachti Levadi" (Yeshayah 63:3) - stomping grapes in the Yekev; 50 refers to 50 Bas (a Bas is three Sa'im).
Targum Yonasan: Fifty barrels of wine. Radak - 10 and 20 are not precise. Sometimes he finds only half, or a little less or a little more. In any case, the curse is recognized.
Why does it discuss bigger measures for the wine?
Rashi citing Avos d'R. Nasan: There is a big need for wine. When it is stricken, it is a bad sign for the world. 1
What is the significance of getting 20?
Rashi: Do not say that the wine was cursed more than the grain (the grain measured half of what was expected, and the wine only 40%). Rather, people err in measuring the Yekev, for it is deep 1 . The stack is in front of him.
Really, it should have measured 40; he drew only 20 due to the curse. (PF)