Concentration risk is the chance that one holding is a big enough slice to decide your result on its own. It rarely arrives as a decision. It arrives through weight drift: a holding that rises faster than the rest takes up more of the portfolio every month, without you buying a single extra share.
So your position size is set by the market as much as by you. The trade-off runs both ways: trimming a winner limits the damage if it falls, and also limits the gain if it keeps going. There isn't a correct size, only one you'd be comfortable with if that holding halved. Each holding's weight is shown in its detail view, and a Pie Chart of your stock portfolio shows them all at once.
No new money and no decision — just drift.
Educational content only. It is not personal financial advice.