maximum and minimum coordinates

Please take a look to the following code:

Graphics3D 640,480 
SetBuffer BackBuffer() 

Global minx#, miny#, minz#
Global maxx#, maxy#, maxz#

camera=CreateCamera() 

light=CreateLight() 
RotateEntity light,90,0,0 

modelname$ = "mak_robotic.3ds"

staticmesh% = LoadMesh(modelname$)
If staticmesh <> 0 Then PositionEntity camera,0,MeshHeight(staticmesh)/2,-MeshDepth(staticmesh)*3
FreeEntity staticmesh

; Load mesh 

animmesh% = LoadAnimMesh(modelname$)

; alpha entity
ent = animmesh

notinit%=True

While ent
	If EntityClass(ent)="Mesh"
		For si=1 To CountSurfaces(ent)
			surf% = GetSurface(ent, si)
			For vi=0 To CountVertices(surf)-1
				x# = VertexX(surf, vi)
				y# = VertexY(surf, vi)
				z# = VertexZ(surf, vi)
				If notinit=True
					minx = x
					miny = y
					minz = z
					maxx = x
					maxy = y
					maxz = z
					notinit = False
				Else
					If x < minx Then minx = x
					If y < miny Then miny = y
					If z < minz Then minz = z
					If x > maxx Then maxx = x
					If y > maxy Then maxy = y
					If z > maxz Then maxz = z
				EndIf
			Next		; vi
		Next			; si
	EndIf
	ent = NextChild(ent)
Wend

Animate animmesh

While Not KeyDown( 1 ) 

	RenderWorld
	UpdateWorld
	If CameraPick(camera, MouseX(), MouseY()) Then Text 0,0, "Picked"
	Text 0,20,"min: "+minx+","+miny+","+minz
	Text 0,40,"max: "+maxx+","+maxy+","+maxz
	Flip 

Wend

FreeEntity animmesh

End


Function NextChild(ent)
	Local siblingcnt
	If CountChildren(ent)>0
		Return GetChild(ent,1)
	EndIf

	Local foundunused=False
	Local foundent = 0, parent,sibling
	While foundunused=False And ent<>0
		parent = GetParent(ent)
		If parent<>0
			If CountChildren(parent)>1
				If GetChild(parent,CountChildren(parent))<>ent
					For siblingcnt = 1 To CountChildren(parent)
						sibling = GetChild(parent,siblingcnt)
						If sibling=ent
							foundunused = True
							foundent = GetChild(parent,siblingcnt+1)
						EndIf
					Next
				EndIf
			EndIf
		EndIf
		ent = parent
	Wend
	Return foundent
End Function

Ultimate Unwrap3D gives me different values:
min: -11.717, -0.697, -9.948
max: 9.026, 47.521, 12.299

I suppose somewhere I make a mistake. But I don't know where