To add to what Tammy had mentioned, here is the detailed information for this option:
mouseover_preview_delay_time:
Specifies the delay time, in milliseconds, between hovering the mouse cursor over an object link and the display of the mouseover preview. The preview is not generated if the mouse is moved away from the link before the delay time expires. Enter a value from 100 to 5000 in the Option Value field.
Default Value: 1000
Thanks,
Naveen