Split function works on first 'space' it finds on the sting - ideally its working correctly based on your Product Name column - technically splitting any text after first 'space'
In order to define correct split - custom split will have to be established : String Functions Refer to this link which explains more on Split function.
Hope this helps.
Custom splitting is splitting the field after first space. Now your second split data type is integer. So when your second split result in an integer, you are getting correct value. But when it is a sting , Tableau not able to convert it to integer and you are getting NULL.