http://developer.yahoo.com/yql/guide/paging.html
Quote
The maximum number of items returned by a
SELECT
is 5000. The maximum processing time for a YQL statement is 30 seconds. For most tables, the default number of items returned is 10. (That is, the default is 10 if you do not specify a limit in theSELECT
statement.)
So 10 results is a default behaviour, if you want more, specify another limit
value.