How do Blitz3D assigns work?

Graphics3D 1024,768,32,1

Global cube1,cube2
camera=CreateCamera()
light=CreateLight()

cube1=CreateCube()
cube2=CreateCube()
PositionEntity cube1,0,3,10
PositionEntity cube2,2,4,10

SetBuffer BackBuffer()


While Not KeyHit(1)
Magnitude#=EntityDistance(cube1,cube2)
Magnitude#=1/Magnitude#

If MouseDown(1) Then MoveEntity cube1,.1,0,0
If MouseDown(2) Then MoveEntity cube1,-.1,0,0


UpdateWorld
RenderWorld
Text 100,100,Magnitude#
Flip
Wend
End