the reason why some people who had applied is still suck in pending while others who applied later turned into IP is we are all applying for different categories under PR application even if it's gonna be still going into process in order of the receipt under the same categories.
ex) International graduate vs family stream vs post-graduate worker vs etc.........
bottom line is it is good to compare dates on each other to get an idea in terms of big picture but if you are counting every single day from someone who applied on the same day with you, it's meaningless unless you two are exactly under same categories of PR application..