Hmmm! I'm sure there is a formula to estimate how many running feet of coverage you get, but I'm not sure. My reflex answer is, "more than you think you'll need". I'd rather have a tube left over than run and ounce short. I resealed a 150, 72"x20"x24" and I think it took three 10 oz tubes.
One word of caution. If you use the SCS-1200, it is super strong, but cures faster than you other silicones. Have every thing set up and ready to go, then get at it, smoothing the seam every so often as you go. Otherwise it may get too stiff to work out.