$FIL |5-minute volume surged 10.1x|Price barely moved
Before looking at position size, first understand volume surges.
At the minute level, spikes in trading volume tend to be noisy. A volume surge in one or two candlesticks may simply reflect a burst of concentrated trading; several consecutive high-volume candles are more informative.
Whether volume rises during a breakout is often considered one factor in judging whether the breakout is valid: breakouts on declining volume are more likely to fail.
Extreme readings often signal greater volatility. At such times, it’s better to reduce your position rather than add to it.