0 - 5 of 5 tags for top

I am trying to get the top 20% of a larger grouping of items;
For example

Every time I select the Top 10 rows of a table I get different results.  I thought the Top function return the exact order that the records were stored in the database table.  I have a data issue I'm attempting to pin down but dont know which record it is and its not helpingif the result are continuously changing.  Is there a better way?

I have a small database to keep track of weekly scores.  Each participant can have 2 or more scores each week.  Some players don't play every week and have no scores for those weeks.  I have the following tables:
Person:  pid, pname
Week: wn, CalDate
Scores:  wn, pid, score

On Viewpoint Query Monitor's Top Sessions Graph of the Summary view, two metrics are represented:  one by the length of the bar and the other by the color or shading of the bar.  The user chooses a metric left of the graph.  How is that metric displayed (length of bar or color/shading)?  What is the other metric?

Hi all
I'm new to teradata I want to confirm about the order priority of the execution of the query.
Sample query
 
Select top n x_column, y_column, z_column from table_abc order by x_column desc;
 
for the above mentioned query what is the order priority of the execution.