Shammai said from one Kav for Challah and Hillel said from two Kavim - שמאי אומר מקב לחלה הלל אומר מקביים
Summary:
הלל maintains that חלה be taken from an עומר (which is two קבין), while שמאי maintains from half an עומר (since the עומר was used for two meals).
אלא שלא דנו דיני נפשות -Rather they did not judge capital cases
Summary:
There is seemingly no requirement for the סנהדרין to be in the לשכת הגזית in order to try (capital) cases. There is no requirement that the סנהדרין be in the לשכת הגזית when the transgression is done.