OK lets use simple numbers to keep it simple...

Lets pretend it takes a total of 1,000 shares to find 1 block (and to keep it simple, we'll pretend that it always takes 1,000 shares)
If you mine and submit 10 shares (and you then stop mining):

You get 1% of the payout in block 1
and
You get 0.5% of the payout in block 2
and
You get 0.333% of the payout in block 3
and
You get 0.25% of the payout in block 4
and
You get 0.2% of the payout in block 5

All for those 10 shares of that 1st needed 1,000

Note:None of these numbers are real and only for demonstration of how the system works.