The number at the bottom is the amount of carbs for one serving.
The first one has 122 grams of carbs for a serving of 450 grams weight.
The second one has 103 grams of carbs for a serving of 370 grams weight.
Do you use an insulin to carbs (I:C) ratio?
Assuming you do, you'll need to know the weight of the serving you are eating and use your ratio to calculate your dose.
If you eat a smaller portion than the serving mentioned, your dose should be adjusted accordingly.
Mind, pizza is notorious with diabetics to be difficult to dose for, so don't get disheartened if even a perfectly calculated dose doesn't result in perfect blood glucose. If you make notes of your dose, how much pizza you had, and how it affected your bg, you might be able to adjust based on experience next time you'll have pizza.
Enjoy!