Can you drop the "15 day Money Back Guarantee" and replace it with 30 day?
The reason is this: A 30 day Money Back Guarantee is a well-used, existing schema that all people are familiar with. It is like tying your shoelaces -- it evokes already existing thoughts and ideas.
Now, when I see
"15 Day Money Back Guarantee!" this immediately violates my schema and my expectations.
It is perceived less than normal.
Normally, violating existing perceptions of your customers is a good thing if it serves a positive purpose or conversion goal. In this case, it doesn't. I immediately think
"Uh oh, whats wrong with this product that he can only give a 15 day money back guarantee?" "Why is it less than 30 days?"
You post this guarantee as a benefit with the anticipation that it improves conversion -- I will argue, it will decrease it. Remove it entirely or up the ante to 30 days.
(Or just say "money back guarantee" and delineate the 15 days in your terms/user agreement).