Why tax is not calculating properly?

bonjour aimerais savoir pourquoi les taxe ne fonctionne pas bien ????

I have checked this form http://www.jotform.ca/form/40636301521240 and I can see it is calculating properly the tax value. 

Here is a screenshot of the tax you have specified in your settings:

Here  is the result: 

Is this the form you're referring to? 

If it is another form, please provide us the form where you're experiencing issues, we will be glad to further check it for you.