Yes, it's quite simple really. R is the inverse of the conductivity and A is the device area. So, if we let "a" be the size of the unit cell,
RA = a**2 / (cond_up+cond_down)
One should be a little bit careful since the conductivity doesn't actually change if we double the unit cell in XY (because we are computing the conductance, not the conductivity), but RA would in the formula above. Thus we should interpret "R" as "per unit cell", and therefore "a" should correspond to the minimal unit cell.