If you're referring to the percentages on your portfolio page, they're just ratios. "Database exposure represents the percentage between your online images vs. the total database at a given date. Not to be mistaken for the Portfolio Exposure (compared to the Top Contributor)"
So the more photos you have online, the higher your DB and PF exposure ratio; but since there are over 8M photos online, and some very busy contributors, these ratios are not likely to become huge.
If you want to generate traffic to your portfolio, which will be measured by the number of views you have on each photo, follow Maen's advice, upload quality pictures, work carefully on your keywords and join in the various conversation of this community (check out message boards, look for photo requests, write blogs...). Good luck!
