Copied from the manual
" A range is not successfully taken. This may happen because the target is beyond the range capability of the scope (either too far or too close), or the range cannot be correctly determined for other reasons. To indicate this result the scope will flash the bottom segments of the four range digits
(_ _ _ _) and display the “Range Fault” pattern for the selected table. The “Range Fault” pattern illuminates dots in 100-unit intervals out to 1,200 units (100-1,200 yards or meters) using the currently selected Table. Many Tables are not capable of reaching 1,200 units. If this is the case, the Dot Pattern will end at the highest 100 unit available. This display also will be corrected for the actual magnification setting. Everything except the dots will go out after 10 seconds; all the dots will remain for the entire 90 seconds."