At the Specific Level, the figure is accentuated against the ground and the range of guessing is narrower.
When the stimulus lasts longer, or is stronger, the figure is strengthened in its definition, and the ground is muted even further. There is the illusion that the figure is actually placed "in front" of the ground.
Examine the classic reversible figure-ground figure in the right column. Notice that if you make the white Chalice the figure, it appears to be in front of the black background; but if you make the two Faces the figure, they (in black shadow) appear to be in front of the white background.
(Please view the illustration in the graphic version here.)
The range of guessing at the Specific level is much narrower than before. We might, for example confuse Mary for Betty, but not for a bush. Hence the percentage of right guesses is higher than at the generic level.