My Adversal is also really low. I contacted them and they gave me the following reasons:
- I use SSL. Adversal doesn't load in SSL.
- Users may be browsing, but not clicking too many links (therefore not setting off popunders).
Another reason may be that the ads are spread out, so a users will not get them every impression (however on my proxies it seems to throw out all 15 or so popunders right away).