How to interpret the rankings of the "site:www.mydomain.com" query?

If i search in G for "site:mydomain.com" there is a certain ranking of my pages.

What defines this ranking?

My best ranked page with the best backlinks is only on page 2, while other weak pages without ranking and with spun content are on page 1....

I don't think they are ranked in accordance with their organic rankings though it does appear that popular pages appear at the top.