It's what I thought - from this page (italics in the text below are mine):
http://www.irs.gov/publications/p502/ar02.html
How Much of the Expenses Can You Deduct?
You can deduct only the amount of your medical and dental expenses that is
more than 7.5% of your adjusted gross income (Form 1040, line 38).
In this publication, the term “7.5% limit” is used to refer to 7.5% of your adjusted gross income. The phrase “subject to the 7.5% limit” is also used.
This phrase means that you must subtract 7.5% (.075) of your adjusted gross income from your medical expenses to figure your medical expense deduction.