Days to cover can spike for two broad reasons: reported short interest rises, or average daily volume falls.
Sometimes both happen at the same time. That is why the ratio can move sharply even when the raw short-interest number does not look especially dramatic on its own.
If the reported short position grows while trading volume stays flat, the days-to-cover reading can move higher.
That often makes sense and can reflect a more crowded short position relative to normal trading activity.
Days to cover can also jump when average daily volume drops sharply.
That is why very high readings should be checked carefully, especially in thinly traded names. A dramatic ratio can sometimes say more about liquidity than about the size of the short position itself.
Use days to cover alongside raw short interest and average daily volume.
If a stock has a high reading because both short interest is large and trading volume is light, that can be more notable than a reading driven mainly by one temporary volume swing.
On ranking pages, some extreme edge cases may be filtered to keep the default leaderboard more readable. That does not mean those values are unimportant. It just means they often need more context than a simple top-line ranking can provide.