problem in permalinks when add new posts

Hello There,
When I Tried to add posts with the same name but in different categories it gives me the permalinks with with number where my permalink is Custom Structure >>>> /%category%-%postname%/
The post is given as :
http://www.test.t/z-test
http://www.test.t/x-test-1
http://www.test.t/c-test-2
and so on
where Z , X,C Are The Category name
& after Posting When I tried to delete the numbers it didn’t deleted.
I hope you get what i say .
Sorry For My Bad English