cellsPerParticle_

Hi,
Is there any particular reason that the voidFractionModel class field cellsPerParticle_ is a 2D array?

When I searched trough the whole CFDEM project it is always present in following context:
cellsPerParticle_[index][0]

except when this table is allocated:
...dataExchangeM().allocateArray(cellsPerParticle_,1,1,nP);