problem with quantity problem

[jacobian64]

hi there, I am having problem with quantity button in my prestashop site. if I went into the checkout page then it look like this below.
 


but after I click the quantity button in the site then the quantitiy button changed into like this



can you tell me what's wrong with my checkout page that it make the quantity button changed itself like that?
this is my site

any help would be appreciated

thanks

[JeredBolton]

The problem is with the javascript that updates the quantity when you click the plus or minus buttons.

 

Compare the javascript you've got with the default theme to see what the differences are.