Note that the question was basically "which of the following influenced your decision to turn down a job offer", not "what was the primary reason you turned down a job offer."

Respondents could select more than one reason; it could be that many of these people had a more important reason for turning down the job like "child care obligations" or "the job didn't offer enough hours of work", but also selected "I receive enough money from unemployment" because that was one of the secondary factors they considered.

They also only polled 463 people and are extrapolating the 1.8 million number based on the fact that 13% (~60 people) included "unemployment insurance" as one of the factors that influenced their decision.