The ratio is a crude measure of crowding. A high figure means shorts cannot exit without moving the price, which is the fuel in a short-squeeze. It is built from two lagged inputs, though: short-interest reported twice a month with a delay, and a volume average that collapses in relevance the moment a stock starts moving.
In a live squeeze volume can run ten times normal, so a ratio of 9 computed on quiet-period volume may be under 1 in practice. Use it as a screen, not as a countdown.
Example: 24M shares short against 3M shares of average daily volume gives 8 days to cover. If volume jumps to 30M a day during a squeeze, the same short position is under a day of real trading.
Related: short-interest, short-squeeze, utilization-rate, float-rotation, hard-to-borrow