Actually the largest integer is 2147483647, after that it goes negative. Yours just overflows into this number.
The red is just because the code isn't designed for such high life values, something must be glitching / overflowing there. It's always happened when fiddling with the console so I just leave it there.
If you wanted to make a save, you could only go up to 65535 though. After that it won't save.