Partially-contained events are similar to fully-contained, in that they originate in the central volume of the inner detector. In partially-contained events, however, one or more particles penetrate far enough to leave the detector, and hence their energy cannot be reliably measured. Due to the showering behavior of electrons, 98% of the tracks which escape the detector (i.e. are only partially contained) are muon-neutrino interactions.
However, considering both the partially-contained events and the fully-contained data at energies above the cut chosen for the sub-GeV sample, an independent "multi-GeV" (higher energy) dataset can also be compared with expectation. Again, roughly third of the expected muon-neutrino interactions are missing. Moreover, at these energies, the anomaly becomes much stronger for neutrinos arriving from below the detector (i.e. those which have travelled a large distance through the Earth.