What does the QTY tag on the Watchlist indicate?

The QTY tag next to a stock on your Watchlist shows how many shares of it you currently hold in your Holdings.

Watchlist showing a QTY - 4 tag next to AFFLE, indicating 4 shares held

The QTY tag only appears for stocks you actually hold. For the other badge you might see on a Watchlist row, see What does the Event tag next to a stock indicate?.