Getting Glass Cut Question

[Marquiseo]

So my tank cracked yesterday. I am either going to replace the back, buy a pre-built tank, or make a new tank. I will weigh the costs. If I go the make one route, I need to make sure the dimensions are spot on.

DIY tank dimensions:

10mm Glass 36"x24"x16"

Glass pieces to cut:
Bottom: (1) 36"x 24" Regular glass
Sides: (2) 16"x24" Low Iron
Front/Back: (2) 36"x16" Low iron/Regular Glass


My question is will I have to add 20mm from the one highlighted in red so that the tank will silicone properly? I may just be over thinking this.
Side pieces are inside the front and back piece.

 

[Reefing Madness]

Just measure the front piece of glass, it should be the same dimensions as the back, and you can plainly see the measurements.