“Up 20%” is half a sentence. Up from what, and since when. Without the base and the window a percent change cannot be read, and a good share of dashboard confusion comes from leaving one of them out.
The base
A percent change is the difference between two values divided by the earlier one. The earlier value is the base. Change the base and the same present value produces a different percentage. A price can be up sharply against last week’s low and down against last week’s high at the same moment. Both statements are true. They answer different questions.
Small bases produce dramatic percentages. Open interest that goes from almost nothing to a modest sum shows a huge percent gain and means very little. A percent change on a tiny base should always be read beside the dollar figure.
The window
The window is the time between the two values. A day, a week, since the close, since the record began. A change with no window attached usually means 24 hours on a crypto screen and since the prior close on a stock screen. Those are different windows, and a market that trades around the clock makes the difference visible.
On a Sunday a stock perp has both. Its 24-hour change covers Saturday into Sunday. Its change since the cash close covers everything since Friday afternoon. Since the cash close explains the second.
When the record is shorter than the window
A window can only be as long as the data behind it. If a record began thirteen hours ago, a figure labeled as a 24-hour change is really a thirteen-hour change. The label is wrong even though the arithmetic is right.
NoVo’s collector began recording stock and index perps on 4 October 2026. An open-interest change is measured against the reading nearest 24 hours back. When the record is younger than that, it is measured against the oldest reading there is, and the true span is shown. The same rule applies to averages, which carry the span the record really covers. The open interest history the venue does not serve explains why the record starts when it does.
Two arithmetic traps
Rates cause their own trouble. If funding moves from 5% a year to 10%, it rose five percentage points and it also doubled. Both are correct descriptions. Saying funding is up 100% without saying which is meant invites a misreading. For rates, points are usually the clearer unit.
Percent changes over consecutive windows multiply. They do not add. A fall of half followed by a gain of half leaves a value at three quarters of where it began. This is the arithmetic behind the slow recovery from a drawdown, and it matters whenever daily changes are strung together into a longer story.
A short checklist
Before reading any change: find the base, find the window, check that the record covers the window, and look at the absolute size. If any of the four is missing from the screen, the number is unfinished. What a percentile window means applies the same discipline to rankings.
Where NoVo shows it
On the Crypto Market Map, the Stocks On-Chain tab shows each perp’s 24-hour change and its open interest with its change. Trader shows the index perps’ move since the last cash close while the cash market is shut.