The _top skin is only for page 1, no matter how many you set in the box. Since you list 100 per page, that would be the max.
This feature is still a takeover from the aardvark days. Originally it was used to make the top x members stand more out, usually 3-5 or so.
Not looked at that function at ages, but i would like it if it works on page 2 etc also ( so, respecting what you set in admin ). Should be doable without much code changes.
Ill have a talk with Mark later on regarding this change