Its just a number. Everyone knows that they have no intention to pay it back. Even if you add 10 more zeros it will have no impact since its worthless.
0*19600000000000 = 0
0*19600000000000000000 = 0
You can add as many zeros you want and it's still just worth what you are paying back, in other words 0
That is the spirit. There is no way the debt will be paid back. The debt will be inflated away, as many governments do in the past centuries.