Why number of matches in fulltext search get less when we put less strings?
Maybe more than 50% of your tablerows contain words starting with "resta*".
Words that are present in 50% or more of the rows are considered common and do not match.

So you would only have those rows returned, that have a non-common word also starting with "resta*" in your result.

see: http://dev.mysql.com/doc/refman/5.5/en/fulltext-natural-language.html

Try 

SELECT * FROM tableauxiliary WHERE MATCH (FullTextSearch)
AGAINST ('resta*' IN BOOLEAN MODE)


see http://dev.mysql.com/doc/refman/5.6/en/fulltext-boolean.html

Boolean full-text searches have these characteristics: - They do not use the 50% threshold that applies to MyISAM search indexes 

I got this here:
Why does MATCH() give Score 0, if there are less rows in the database?