This scanning message appears if Q++ notices that there is a [GenTokens] token on the first line of a textbox. This will cause unexpected results, as QuarkXPress ignores the leading of the first line of a textbox, as shown in the example below, which shows 2 textboxes one with all lines of 18 points leading and the other with all lines of 48 points leading.

As one can see, the baseline of the fistr lines of both textboxes is exactly the same, although leading should specify the distance from the previous line (actually, the right textbox's text will move down if you add some rule above value, further compounding the problem).
Therefore it is safer to never place GenTokens tokens on the first line of a textbox.
Note that the first line of a textbox is defined as any text occurring before the first hard return; the presence of a soft return alone will not stop this message from being generated.