To what I could understand, they've separated it out to avoid confusion regarding points calculation's on work experience.
which means if you have work experience for 5 years you get 10 points in total.
But the number of years experience beyond 5 years will give you 1 additional point.
suppose for e.g. 6yrs=11, 7yrs=12 and soo on, max the experience points you can claim is 15.
It doesn't matter the occupation you need to show the number of total experience within last 10 years.
Regarding the Occupation part you'll need to get the reference letters for the years of experience you've stated here and they needs to be uploaded stating NOC codes once you start filling on Oasis portal.