In short, you need to delete ALL of the sample/test data like orders,customers and products.
Now the question, Is there a built in feature to get rid of it all so that they all go and when you start creating things they start at record 1? If not, is there a bare install that doesn't install any sample data as you don't need it or want it.
Now the solution for delete all of the sample/test data is below :
1. Go to back office--> modules--> in search box type cleaner
2. install the pscleaner module
But, don't forget to backup you database first if you dont want to install it again.