In answer to your question, and I quote from Billboard.com;
"It's a common misconception that certifications are based on sales to consumers. The RIAA issues gold, platinum, and now diamond certifications based on the number of units shipped to stores. So your favorite artist's latest album shipped three million copies, which is why it's already certified platinum even if all three million copies haven't passed into consumers' hands yet.
Certifications aren't automatic; labels must request and pay for them. So if five older albums were all certified at once, it just means the label decided to apply for all five at the same time, not that they all crossed the million-mark in the same month."
Edit - If they shipped 750,000 and already paid for the gold certification, then I guess that answers my question on what they expect to sell