gengeo question: BoundingBox Size in *.geo was different from what was set in MNTable3D

Question BoundingBox Size in smooth_box.geo was different from what was set in MNTable3D
In smooth_box.geo: BoundingBox 0 0 0 10 10 10
the value in MNTable3D: maxPoint 8 8 8

# --- geometry setup script for monodisperse packing with particle at regular postion ---
from gengeo import *
from math import *
# - input parameters --

#'''
# radius
minRadius = 0.4
maxRadius = 2.0
# maximum number of particle in three directions
N_X = 10
N_Y = 10
N_Z = 10

# atuo_cal block dimensions
## adopt float!
xdim=N_X*2.0*minRadius
ydim=N_Y*2.0*minRadius
zdim=N_Z*2.0*minRadius

#

# ---------------------
# corner points
minPoint = Vector3(0.0,0.0,0.0)
maxPoint = Vector3(xdim,ydim,zdim)
# neighbour table
mntable = MNTable3D(minPoint,maxPoint,2.5*maxRadius,1)
# block volume
box = BoxWithPlanes3D(minPoint,maxPoint)

# boundary planes
bottomPlane=Plane(minPoint,Vector3(0.0,1.0,0.0))
leftPlane=Plane(minPoint,Vector3(1.0,0.0,0.0))
frontPlane=Plane(minPoint,Vector3(0.0,0.0,1.0))
topPlane=Plane(maxPoint,Vector3(0.0,-1.0,0.0))
rightPlane=Plane(maxPoint,Vector3(-1.0,0.0,0.0))
backPlane=Plane(maxPoint,Vector3(0.0,0.0,-1.0))
# add them to the box
box.addPlane(bottomPlane)
box.addPlane(leftPlane)
box.addPlane(frontPlane)
box.addPlane(topPlane)
box.addPlane(rightPlane)
box.addPlane(backPlane)

# -- setup packer --
# iteration parameters
insertFails = 10000
maxIter = 10000
tol = 1.0e-6

Particle_number_1 = 0

#generate particle at regular position

for i in range(N_X):
 for j in range(N_Y):
  for k in range(N_Z):

   mySphere = Sphere(centre=Vector3((i+0.5)*2*minRadius,(j+0.5)*2*minRadius,(k+0.5)*2*minRadius), radius=minRadius)
   mySphere.setTag (2)
   mntable.insert(mySphere,0)
   Particle_number_1 +=1

print "Particle_number_1: ",Particle_number_1
#'''
# generate interior particle
# packer
packer = InsertGenerator3D( minRadius,maxRadius,insertFails,maxIter,tol,False)
# pack particles into volume
packer.generatePacking(box,mntable,0,1)
#'''
#'''

#'''
# get ParticleList
particleList = mntable.getSphereListFromGroup(groupID=0)

# remove
mntable.removeParticlesInGroup(0)

Particle_Number = 0
# change the tag
for pp in particleList:
 Particle_Number += 1
 Pcentre = pp.Centre()
 Pradius = pp.Radius()
 X_Posn = Pcentre.X()
 Y_Posn = Pcentre.Y()
 Z_Posn = Pcentre.Z()
 ###
 if ((Y_Posn - 1.5*minRadius) <= 0):#bottom
  pp.setTag(2)
 elif (Y_Posn + 1.5*minRadius>=ydim):#top
  pp.setTag(3)
 elif ((X_Posn - 1.5*minRadius) <= 0):#left
  pp.setTag(4)
 elif ((X_Posn + 2.0*minRadius) >= xdim):#right
  pp.setTag(5)
 elif ((Z_Posn - 1.5*minRadius) <= 0):#back
  pp.setTag(6)
 elif ((Z_Posn + 1.5*minRadius) >= zdim):#front
  pp.setTag(7)
 else:
  pp.setTag(1)
 mntable.insert(pp)
 ###
# create bonds between neighbouring particles:
mntable.generateBonds(0,0.005,1)

print "Particle_Number: ", Particle_Number

#output xdim, ydim, zdim
print "xdim: ", xdim
print "ydim: ", ydim
print "zdim: ", zdim

#'''
# write a geometry file
mntable.write("smooth_box.geo", 1)
mntable.write("smooth_box.vtu", 2)