how is top % filter used?

ok question was stupid i know. i still want to know how the filters work and an example for each filter option would be great. why can't all documentations be like msdn library? the built-in documentation shipping with reporting services is just too advanced for moi.
The Top% filter works similar to the TopN filter. A TopN filter with filter value =10 would return the first 10 values of the dataset - regardless of the total number of rows in the dataset. A Top% filter with filter value =10 would return the first 10% of the total number of rows in the dataset.

-- Robert|||I asked the question because the expression i wrote did not work so thought there was something wrong with my syntax. I finally found out that the reporting services filter does not correctly evaluate datatypes other than strings. So I changed my filter expression to convert the vaule into string first and now they work no thanks to the guy writing documentation. This is a bug and it took me quite a while to figure it out.
|||

The alternative is to make sure it takes the value as a numeric by preceeding it with an equal sign. Without this post I would have spent a long time trying to get this to work.