If you want the sums and display to occur every second that you should only call sevenseg() every second, as it is you're calling it every time loop() is called, maybe 1,000 times a second although all the print()s may slow it down some.
A quick fix
if (mills() % 1000 == 0) sevenseg(number);
But that code is really bad and could do with some work to clean it up.
EDIT: You just want a counter to count down from 1922222222 in seconds, is that the case? If so you realise that will take 60 years?
Rob