how did we get to 7000 in the sequence above and what is the next number?

I dunno, Andre. Here's an answer equally confusing:

(10 + 9 + 90 + 91)*35 = 7000

Then of course keep it up (minus 1, multiply, add 1, etc.):

7000 - 1 = 6999 * 7000 = 48,993,000 + 1 = 48,993,001

so: (7000 + 6999 + 48,993,000 + 48,993,001) * 35 = 3,430,000,000

Whaddya think?