Itemamount and Quantity fields

Can I use fixed numbers for Itemamount and for Quantity, rather than using the field IDs?

For Itemamount could i enter 9.99, meaning 9.99 dollars (presuming I’ve selected dollars as my currency? Or would I need to put the number in quote marks? (The same question applies to quantity – CAN I PRESUME THE ANSWER IS THE SAME?)

https://wordpress.org/plugins/contact-form-7-paypal-extension/