As Robert pointed out, if your max load is considerably less than 100 Amps, you may not want the 100 Amp CT.
I see several posistions in your load center have 15 Amp breakers. However, I see one 50 A double pole breaker and three 30 Amp DP breakers. Which CT to choose, might depend on your house being all-electric, vice having some gas-fired appliances. If your house is all-electric, and it’s not uncommon for you to operate more than one of the large appliances (or many small ones) at the same time, then you’ll likely want the 100 Amp CT. If however, you rarely operate the large appliances at the same time, e.g. one is a heater and another an air conditioner, OR you have gas-fired space/water heating, stove/oven, etc, you’ll likely want a CT with a rating less than 100 Amps.
The next lower rating in the Wattcore WC-3 series is 50 Amps, so deciding on which one to use is going to require some simple “number crunching.”
Take a look at the electrical appliances you use on a daily basis, and read their labels to get an idea of how much power they draw. Add up the numbers on the labels of those you use at the same time, Add 15% to the total for some headroom, and you have your answer.
If it’s more than 50-55 Amps, you’ll want the 100 Amp CT. Less than 50 Amps, choose the 50 Amp CT