Multiple flat rate loops

My flat rate options are like this:

• Airmail - £4 per item in cart
• First class - £1.50 per item in cart
• Second class - £1 per item in cart

I followed the tutorial on here: https://commerceguys.com/blog/using-calculation-rules-add-item-shipping-...

However when I repeat the process, the shipping options just come out identical. How can I offer multiple flat rate options which loop through items in the basket to add varying amounts?