A candle looks like raw data. It is a summary. Somebody took every trade in an interval and reduced it to four prices and a volume. Knowing how that reduction works explains several things a chart seems to get wrong.
Four numbers from many
A candle covers a fixed interval. Its open is the first trade in the interval and its close is the last. Its high and low are the extremes. Volume is the total traded. Everything else about the interval is discarded: the order of the high and the low, how long price spent at each level, how many trades there were. Candlestick basics covers how to read the shape. This article is about how it is made.
Where the edges fall
Intervals are cut on the clock. A 15-minute candle runs from one quarter hour to the next. Which clock is a choice the data provider makes, and so is whether a candle is labeled by its start or its end. Two charts of the same market can show different candles because one is offset from the other. Time zones and the cash close covers the clock side.
The label matters when you need a specific moment. The price at the cash close is the close of the candle that ends at the bell. On a provider that labels by start time, that candle carries an earlier label.
The candle that is still forming
The most recent candle is incomplete until its interval ends. Its close is just the latest trade and its high and low can still extend. Any calculation that treats the forming candle as finished will change its answer when the interval ends. Using an unfinished bar in a test as though its final values were known at the start is a form of look-ahead bias.
An interval with no trades
If nothing trades in an interval, there is no first or last trade, and strictly there is no candle. Providers handle this differently. Some omit the bar and leave a gap. Some draw a flat bar at the previous close. The flat bar keeps the chart tidy and hides the fact that no trade occurred.
For a measurement anchored to a moment this matters. NoVo measures each index perp against its own price at the last cash close, from the 15-minute candle that ends at the bell. If the perp has no print at the bell there is no figure. Carrying an older price into that slot would produce a number built on a stale anchor.
What a bar cannot see
Within the interval, a candle is blind. A spike that reverses inside the bar shows only as a wick. Two candles with identical values can hide opposite paths: high first then low, or low first then high. A stop sitting inside the range may or may not have been reached before a target, and the candle cannot say which.
A candle also says nothing about the quote. It is built from trades. In a thin market a wide spread can sit around a candle with almost no range, and the candle looks calm.
Choosing an interval
Shorter intervals keep more detail and more noise. Longer ones smooth both away. The right choice depends on the question. A reference price at the bell needs a bar that ends at the bell. A view of the week needs fewer, longer bars.
The Stocks On-Chain tab on the Crypto Market Map charts each perp’s recorded open interest, and Trader shows the index perps’ move since the cash close while the cash market is shut.