I think no matter what there will be 10 spots left when you interview. It was kind of confusing, but they wait to fill the last 10 spots until all of the interviews are done so they get a look at everyone. Then they fill in those spots and make an alternate list and rank it. Then they fill any spots that open up with the alternate list. I wouldn't skip the interview unless you really don't think you want to go there and are in at other schools.