...here... the LL line...
centered 120 cubits south
of the south edge of G1
is expanded in width
to 120 cubits wide

(click pix for hi-rez)

LL line 120 cubits wide
north extension = -280
mid: -220 - 120 = -340
south extension = -400

...to meet the edge of S1
...being the sphere of G1
based on its height of 280
n having a diameter of 560

G1 as the model center
north extension = +220
midpoint coords = 0
south extension = -220

S1 as the sphere of G1
north extension = +280
midpoint as G1 = 0
south extension = -280

that's the one on the right...
projecting out from G1 center...
on the left we have its mirror...
with 120 cubits between the pair...

S1m ... S1's mirror...
north extension = -400
mid: -220-60-60 = -680
south extension = -960

...so, a second sphere is introduced
...centered: 680 cubits south of G1
...where, it too, is tangent to...
the LL, line made 120 cubits wide

...but, that's not quite
on the same line with G2

below... S2, G2's sphere is added
G2 center = ( -638.50 , -675.50 )

G2 has a 411 cubit square base
...and its height is... 274.5

thus, S2 is given
a diameter of 549

the red sphere
is a copy of S2
with same cubits
south of G1: 675.5
but due south of G1
so 0 cubits east-west

S2m = ( 0 , -675.5 )

the cage around it is
the first mirror: S1m
(cloud texture above)
...moved onto G2's line
so... 680 - 675.5 = 4.5
(notice it's half of 9)
keeps S1's 560 diameter
but now moved to align
to that same center...
so, the mirror spheres
...are now aligned...

S1m = ( 0 , -675.5 )

G1m new positionings...
north extension = -395.5
mid: -220-60-60 = -675.5
south extension = -955.5