This is about short term (ie, a few days, or 1-2 weeks trend).
When a stock is in a uptrend (regardless it is wave 1 or 3), it usually will create gaps on the way up. The simple way to detect whether this trend still continues, or about to turn (ie, from wave 1 to wave 2, or from wave 3 to wavw 4) is to see if that gap will be filled within 2-3 days.
If a stock fill that gap immediately within 2-3 days, it means this gap is NOT confirmed and the uptrend wave could turn around.
So, if you look at COIN, short term wise, today, if it close below 273, it basically filled the gap and go lower within 2 days, that could signal an end to the current wave. If current wave ended, the retracement is likely take COIN to 0.5 or .618 level (256-237)
However, if we are able to hold 273, COIN is likely to continue with current wave.
This is essentially the same analysis with Tesla, which is why 328 is important on TSLA
