Hilchos Maasei Hakarbanos 2:8

When libations and flour offerings are measured for individual or communal offerings, they are not measured in a three-isaron vessel for a bull or two-isaron vessel for a ram. Rather, everything is measured with the one-isaron vessel that was in the Temple. Similarly, oil for the libations was measured with the appropriate service vessel. The oil for the flour offering of an individual was measured in the one-log vessel in the Temple. The number of logs of oil was based upon the number of esronim of flour.

Hilchos Maasei Hakarbanos 2:9

The flour that overflowed the vessels when measuring was considered secular because the outside of the isaron vessel was not sanctified. However, the wine and oil that overflowed the measuring vessel were considered consecrated because it flows down the back of the vessel, whose inside and outside were both anointed. You might ask why the overflow should be considered consecrated when the one doing the measuring only intended to consecrate the contents of the vessel. The reason is so that people not think that things that had been inside consecrated vessels are then used for secular purposes.