Excellent Chart - Help Adapting

Hi,

I found this amazing chart on the following site:

HTML Code: 

If possible I want to use it for something I am putting together.

the original data only had 5 months - I need to extend this concept to a full 12 months.

I dont know how to add any further months to the chart - when I select data to see where its being picked up from it appears blank - any ideas how?