This pattern is used to say that something does not reach a certain level, but even so, what follows is still true. It often translates as 'not to say that... but at least' or 'even if not...' The first part presents a higher degree or stronger condition, and the second part notes that a lesser but still significant degree applies. For example, you might say that someone is not a genius, but they are still talented. The pattern is somewhat formal and is often used in written Japanese or careful speech. It can also be used to express a concession, like 'even if I don't have the money to buy it, I can at least look.' The key is that the first clause is a hypothetical or unrealized condition, and the second clause states what is still possible or true. Note that the negative form used is the plain negative, not the polite form. Also, the pattern is often followed by expressions like ても or でも, but not always.